Activation Markers Research Articles

A comparative study of blood cell count in four automated hematology analyzers: An evaluation of the impact of preanalytical factors.

Differential white blood cell counts are frequently used in diagnosis, patient stratification, and treatment selection to optimize therapy responses. Referral laboratories are often used but challenged with use of different hematology platforms, variable blood shipping times and storage conditions, and the different sensitivities of specific cell types. To extend the scientific literature and knowledge on the temporal commutability of blood samples between hematology analyzers, we performed a comparative ex-vivo study using four of the most utilized commercial platforms, focusing on the assessment of eosinophils given its importance in asthma management. Whole blood from healthy volunteers with and without atopy (n = 6+6) and participants with eosinophilic asthma (n = 6) were stored under different conditions (at 4, 20, 30, and 37°C, with or without agitation) and analyzed at different time points (3, 6, 24, 48 and 72h post-sampling) in parallel on the Abbott CELL-DYN Sapphire, Beckman Coulter DxH900, Siemens ADVIA 2120i and Sysmex XN-1000V. In the same blood samples, eosinophil-derived neurotoxin (EDN), eosinophil activation and death markers were analyzed. All platforms gave comparable measurements of cell differentials on fresh blood within the same day of sampling. However, by 24 hours, significant temporal and temperature-dependent differences were observed, most markedly for eosinophils. None of the platforms performed perfectly across all temperatures tested during the 72 hours, showing that handling conditions should be optimized depending on the cell type of interest and the hematology analyzer. Neither disease status (healthy vs. asthma) nor agitation of the sample affected the cell quantification result or EDN release. The eosinophil activation markers measured by flow cytometry increased with time, were influenced by temperature, and were higher in those with asthma versus healthy participants. In conclusion, hematology analyzer, time window from sampling until analysis, and temperature conditions must be considered when analyzing blood cell differentials, particularly for eosinophils, via central labs to obtain counts comparable to the values obtained in freshly sampled blood.

Invasive electrochemical impedance spectroscopy with phase delay for experimental atherosclerosis phenotyping.

Distinguishing quiescent from rupture-prone atherosclerotic lesions has significant translational and clinical implications. Electrochemical impedance spectroscopy (EIS) characterizes biological tissues by assessing impedance and phase delay responses to alternating current at multiple frequencies. We evaluated invasive 6-point stretchable EIS sensors over a spectrum of experimental atherosclerosis and compared results with intravascular ultrasound (IVUS), molecular positron emission tomography (PET) imaging, and histology. Male New Zealand White rabbits (n = 16) were placed on a high-fat diet, with or without endothelial denudation via balloon injury of the infrarenal abdominal aorta. Rabbits underwent invivo micro-PET imaging of the abdominal aorta with 68Ga-DOTATATE, 18F-NaF, and 18F-FDG, followed by invasive interrogation via IVUS and EIS. Background signal-corrected values of impedance and phase delay were determined. Abdominal aortic samples were collected for histology. Analyses were performed blindly. EIS impedance was associated with markers of plaque activity including macrophage infiltration (r = .813, p = .008) and macrophage/smooth muscle cell (SMC) ratio (r = .813, p = .026). Moreover, EIS phase delay correlated with anatomic markers of plaque burden, namely intima/media ratio (r = .883, p = .004) and %stenosis (r = .901, p = .002), similar to IVUS. 68Ga-DOTATATE correlated with intimal macrophage infiltration (r = .861, p = .003) and macrophage/SMC ratio (r = .831, p = .021), 18F-NaF with SMC infiltration (r = -.842, p = .018), and 18F-FDG correlated with macrophage/SMC ratio (r = .787, p = .036). EIS with phase delay integrates key atherosclerosis features that otherwise require multiple complementary invasive and non-invasive imaging approaches to capture. These findings indicate the potential of invasive EIS to comprehensively evaluate human coronary artery disease.

Beta-Hydroxybutyrate Mitigates Sensorimotor and Cognitive Impairments in a Photothrombosis-Induced Ischemic Stroke in Mice.

The consequences of stroke include cognitive deficits and sensorimotor disturbances, which are largely related to mitochondrial impairments in the brain. In this work, we have shown that the mimetic of the ketogenic diet beta-hydroxybutyrate (βHB) can improve neurological brain function in stroke. At 3 weeks after photothrombotic stroke, mice receiving βHB with drinking water before and after surgery recovered faster in terms of sensorimotor functions assessed by the string test and static rods and cognitive functions assessed by the Morris water maze. At the same time, the βHB-treated mice had lower expression of some markers of astrocyte activation and inflammation (Gfap, Il-1b, Tnf). We hypothesize that long-term administration of βHB promotes the activation of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) pathway, which leads to increased expression of antioxidant genes targeting mitochondria and genes involved in signaling pathways necessary for the maintenance of synaptic plasticity. βHB partially maintained mitochondrial DNA (mtDNA) integrity during the first days after photothrombosis. However, in the following three weeks, the number of mtDNA damages increased in all experimental groups, which coincided with a decrease in Ogg1 expression, which plays an important role in mtDNA repair. Thus, we can assume that βHB is not only an important metabolite that provides additional energy to brain tissue during recovery from stroke under conditions of mitochondrial damage but also an important signaling molecule that supports neuronal plasticity and reduces neuroinflammation.

CD8+ T-cell differentiation and dysfunction inform treatment response in acute myeloid leukemia

AbstractThe interplay between T-cell states of differentiation, dysfunction, and treatment response in acute myeloid leukemia (AML) remains unclear. Here, we leveraged a multimodal approach encompassing high-dimensional flow cytometry and single-cell transcriptomics and found that early memory CD8+ T cells are associated with therapy response and exhibit a bifurcation into 2 distinct terminal end states. One state is enriched for markers of activation, whereas the other expresses NK-like and senescence markers. The skewed clonal differentiation trajectory toward CD8+ senescence was also a hallmark indicative of therapy resistance. We validated these findings by generating an AML CD8+ single-cell atlas integrating our data and other independent data sets. Finally, our analysis revealed that an imbalance between CD8+ early memory and senescent-like cells is linked to AML treatment refractoriness and poor survival. Our study provides crucial insights into the dynamics of CD8+ T-cell differentiation and advances our understanding of CD8+ T-cell dysfunction in AML.

KLF4 Inhibits the Activation of Human Hepatic Stellate Cell In Vitro.

Hepatic stellate cells (HSCs) play a crucial role in liver fibrosis. Early-stage liver fibrosis is reversible and intimately associated with the state of HSCs. Kruppel-like factor 4 (KLF4) plays a pivotal role in a wide array of physiological and pathological processes. This study aimed to investigate the effect of KLF4 on the proliferation, apoptosis and phenotype of quiescent HSCs METHODS: We designed a KLF4 lentiviral vector and a KLF4 siRNA lentiviral vector, to upregulate and silence KLF4 expression in human HSC LX-2 cells via transfection. Cell proliferation was assessed using the CCK-8 assay. Flow cytometry was used to detect the cell cycle distribution and apoptosis rate. Western blotting was used to determine the levels of some quiescence and activation markers of HSCs RESULTS: Overexpression of KLF4 significantly increased the levels of E-cadherin and ZO-1, which are quiescent HSC markers, while significantly decreased the levels of N-cadherin and a-SMA, known activated HSC markers. In contrast, cell proliferation and apoptosis rates were elevated in LX-2 cells in which KLF4 expression was silenced CONCLUSION: KLF4 inhibits the proliferation and activation of human LX-2 HSCs. It might be a key regulatory protein in the maintenance of HSC quiescence and may serve as a target for the inhibition of hepatic fibrosis.

Celastrus orbiculatus Extract Inhibits Immune Inflammatory Thrombotic State of B-Lymphoma.

To investigate the inhibitory effect of Celastrus orbiculatus extracts (COE) on the proliferation of lymphoma cells and the immune regulation ability on inflammation and thrombophilia in vivo. The 38B9 lymphoma cells were treated with COE (160 µ g/mL) and CTX (25 µ mol/L). The apoptosis rate and cell cycle of each group were detected by flow cytometry. The secretion of inflammatory factors, including interleukin (IL)-6, IL-10, and tumor necrosis factor α (TNF-α), in cell supernatant was detected by enzyme-linked immunosorbent assay (ELISA). In vivo, BALB/c mice were subcutaneously injected with 38B9 lymphoma cells to establish lymphoma model. COE (3 mg·kg-1·d-1) and CTX (40 mg·kg-1·d-1) were administered to the model mice, respectively. The expression of plasma inflammatory factors (IL-6, IL-10 and TNF-α) and thrombus indexes, including D-dimer (D-D), von Willebrand factor (vWF) and tissue factor (TF), were detected by ELISA before tumor bearing (1 d), after tumor formation (14 d) and after intervention (21 d). PicoGreen dsDNA was used to detect the level of serum neutrophil extracellular traps (NETs). Flow cytometry was used to detect the expression of platelet activation marker calcium-dependent lectin-like receptor 2 (CLEC-2). The tumor growth and survival of mice were recorded. The 38B9 lymphoma cells were apoptotic after the intervention of COE and CTX. The ratio of G2-M phase cells decreased in COE intervented cells compared with the control cells (P<0.05), and S phase cells decreased in CTX intervented cells (P<0.05). Also, the secretion level of IL-6 was significantly reduced after COE or CTX intervention (P<0.05), and IL-10 was significantly increased (P<0.05). Furthermore, the tumor mass was reduced, and the median survival time was longer in COE and CTX intervented tumor-bearing mice than in non-intervented mice. The significantly lower levels of TNF-α, IL-6, NETs, TF, DD and CLEC-2, as well as higher IL-10 were observed in COE and CTX treatment mice in comparision with the control mice (P<0.05). COE has a mild and stable anti-tumor effect, which can reduce the secretion of inflammatory factors by lymphoma cells and regulate thrombophilic state caused by tumor inflammatory microenvironment.

MEASUREMENT OF PLATELET ACTIVATION MARKERS CD62P AND CD63 TO DETERMINE THE EFFICIENCY OF DUAL THERAPY WITH ASPIRIN AND CLOPIDOGREL: A PRELIMINARY STUDY

Background: A dual antiplatelet therapy with aspirin and clopidogrel is advised to prevent stent thrombosis. However, the most appropriate assay for evaluating the antiplatelet effects remains undefined. Objective: This study aimed to assess the efficacy of measuring platelet surface activation markers, CD62P and CD63, using flow cytometry to determine the effectiveness of dual antiplatelet therapy. Methods: Thirty patients who received aspirin plus clopidogrel before cerebral artery stent implantation and thirty unrelated healthy controls were enrolled. The expression of CD62P and CD63 was measured using flow cytometry. The diagnostic performances were evaluated and compared with the conventional light-transmitted aggregometry (LTA) using 5.0 and 20.0 µM of adenosine di-phosphate (ADP). Results: The expression ratios of both markers were significantly lower in the patients receiving dual antiplatelet therapy than controls (p &lt; 0.001). The area under the receiver operating characteristic (ROC) curve (AUC) of CD62P using flow cytometry and the LTA using 5.0 and 20.0 µM of ADP were comparable (0.97 vs. 0.95 and 0.97 vs. 0.96, respectively), whereas those of CD63 was lower than the LTA (0.88 vs. 0.96). The sensitivity of CD62P and CD63 were 71.4% and 60.0%, and the specificity of CD62P and CD63 were 100.0% and 96.7%, respectively. Conclusion: Flow cytometry measurements of CD62P could be utilized to identify the efficacy of dual antiplatelet therapy. Additional studies are suggested to support this issue and its effects on clinical outcomes.

#2396 The potential of human-derived macrophages to study autosomal dominant polycystic kidney disease (ADPKD)

Abstract Background and Aims Macrophages are the most prevalent immune cell type in the renal parenchyma in ADPKD. Depletion of macrophages in animal models has shown a dramatic attenuation in cystic burden, suggesting a disease promoting effect of this cell type. So far, studies investigating interaction between epithelial cells and immune cells in the field of ADPKD were performed with mice-derived myeloid cells. We present a new model using human-derived immune cells and tubular epithelial cells for the study of ADPKD. Method We established a technique to isolate CD14+ monocytes from the peripheral blood of young ADPKD patients and healthy controls. Methodology was optimized to create monocyte-derived macrophagesin vitro. Mature macrophages were checked for surface marker expression (CD14, CD11b, CD206, CD163, HLA-DR, D80, and CD86) &amp; cytokine-release after stimulation with LPS, IL-4 and LPS + Nigericin. Co-cultures were performed using human-derived monocytes in combination with double immortalized cystic cells (ciCC) or healthy-kidney derived cell lines (HKT). Differentiation and polarization of macrophages was checked using flowcytometry. Results We observed low expression of PKD1 and PKD2 transcripts in primary, human-derived monocytes of ADPKD patients and controls. The expression of PKD1 and PKD2 increased after differentiation into macrophages. There were no clear differences between ADPKD and control-derived macrophages in the differentiation capacity, cell survival nor surface marker expression before and after differentiation. After stimulation with LPS &amp; LPS + Nigericin ADPKD-derived macrophages showed significantly lower expression of pro-inflammatory cytokines (MIP-1α, IP-10, IL-23 and TNFα) as compared to controls. There was no difference in anti-inflammatory cytokine release. Healthy primary monocytes cultured in direct contact with conditionally immortalized cystic cells (ciCC) had a very good survival and showed differentiation into macrophages with high expression of M2-markers (CD163 and CD206) and the activation marker (HLA-DR). A similar differentiation pattern was seen when monocytes were cultured in the (cell-free) conditioned medium of the ciCC harvested after 72 h, pointing to a soluble factor produced by the cystic cells that induces monocyte differentiation and macrophage polarization. In accordance, unbiased multiplex cytokine analysis (Target 48-panel) of supernatants of ciCC, showed higher levels of macrophage colony-stimulating factor (M-CSF/CSF-1), TNF-α, hepatocyte growth factor (HGF) and MMP-1 as compared to those of HKT. Primary monocytes cultured with the conditioned medium harvested after 72 h from ciCCs (n=4) showed better overall survival than those cultured with medium from and HKT (n=4). In addition, a tendency towards higher expression of the classical M2-markers (CD163, CD206) and the activation marker (HLA-DR) in ciCCs versus HKT was seen. Conclusion There is wealth of data supporting the indispensable role of myeloid cells in disease progression of ADPKD. We established a unique in vitro fully human co-culture model for ADPKD. Cystic cells produce pro-proliferative and pro-angiogenic factors, thus actively shaping their microenvironment and creating the ideal circumstances for infiltrating monocytes/macrophages to proliferate and to destruct the kidney. This mechanism is very similar to what is seen in the cancer microenvironment. Further experiments will help to elucidate the complex interplay between different cell-types in the microenvironment in ADPKD kidneys.

#1467 Pegcetacoplan for post-transplant recurrent C3 glomerulopathy or immune complex membranoproliferative glomerulonephritis in NOBLE: 12-week evolution

Abstract Background and Aims C3 glomerulopathy (C3G) and primary immune complex membranoproliferative glomerulonephritis (IC-MPGN) are rare diseases caused by uncontrolled complement activation, resulting in excess deposition of C3 breakdown products in the kidneys, which leads to kidney damage and eventually kidney failure. Kidney transplantation is an option for end-stage kidney disease, but disease recurrence is common (up to 67% of patients), and up to 50% of transplant recipients lose renal allografts due to recurrence. Pegcetacoplan is a targeted C3 and C3b inhibitor that may prevent excess deposition of C3 and C5 breakdown products and subsequent glomerular inflammation and kidney damage in patients with C3G or IC-MPGN, potentially improving clinical outcomes. NOBLE (NCT04572854) was the first prospective randomized controlled trial of pegcetacoplan vs standard of care (SOC) in post-transplant patients with recurrent C3G or IC-MPGN. Method Adult patients were randomized 3:1 to subcutaneous pegcetacoplan 1080 mg twice weekly plus SOC (n = 10) or SOC only (n = 3) for 12 weeks followed by a 40-week non-controlled period in which all patients received pegcetacoplan. Primary and secondary endpoint results for Week-12 data have been reported. We conducted a patient-level post hoc analysis to describe key histology changes from renal biopsy (C3c staining, C3G histologic index activity score), clinical parameters (urine protein-to-creatinine ratio [uPCR; calculated from triplicate first-morning spot urine], estimated glomerular filtration rate [eGFR]), and biomarkers (serum C3, plasma sC5b-9) through Week 12. The C3G histologic index uses a semiquantitative scale of 0–3 for 7 markers of activity (mesangial hypercellularity, endocapillary proliferation, membranoproliferative morphology, leukocyte infiltration, cellular and/or microcellular crescent formation, fibrinoid necrosis, and interstitial inflammation), for a total activity score of 0–21. eGFR stability was defined as a decrease of no more than 25% versus baseline. Results Among the 10 pegcetacoplan-treated patients, 7 (70%) had 1 previous kidney transplant, 2 (20%) had 2, and 1 (10%) had 3. The mean (range) time to disease recurrence after most recent transplant was 10.8 (0.4–31.8) months and from most recent recurrence to randomization was 12.2 (2.1–37.7) months, with 60% randomized &amp;gt;6 months post-disease recurrence. Among the 3 SOC-only patients, 2 (66.7%) had 1 transplant and 1 (33.3%) had 2. Mean (range) time to recurrence was 32.8 (4.6–63.8) months and to randomization was 33.9 (7.0–65.4) months. At Week 12, 8 (80%) pegcetacoplan-treated patients had a reduction in C3c staining of at least 1 order of magnitude. Of these 8, 7 (70%) had a decrease in activity score, and 6 of these 7 (60%) had a decrease in proteinuria. Four (40%) patients had reduced C3c staining, decreased activity score, and cleared electron microscopy deposits at Week 12. eGFR remained stable in 9 (90%) patients. Six of 9 (67%) patients with available Week-12 data (4 of 5 patients with &amp;gt;1 g/g uPCR at baseline) had a reduction in uPCR with 5 of the 6 achieving ≥50% uPCR reduction (Table). All pegcetacoplan-treated patients had increased serum C3, as expected, and 9 (90%) had decreased sC5b-9. At Week 12, no TEAEs led to study discontinuation, treatment withdrawal, or death. No encapsulated bacterial infections or events of rejection/graft loss related to the study drug were reported. Conclusion As early as Week 12, more than half (6/10 [60%]) of post-transplant patients with recurrent C3G or IC-MPGN treated with pegcetacoplan achieved reductions in C3c staining, activity score of C3G histology index, and proteinuria, suggesting that pegcetacoplan targets the underlying pathophysiology of the C3G/IC-MPGN in kidney transplant recipients. The safety and efficacy of pegcetacoplan will be further evaluated at Week 52 of the NOBLE study and as part of the Phase 3 VALIANT (NCT05067127) trial, which enrolled patients with C3G or primary IC-MPGN who have native kidney or post-transplant disease.

#417 Targeting parietal epithelial cell activation with mineralocorticoid receptor antagonism controls FSGS and crescentic glomerulonephritis

Abstract Background and Aims We have recently demonstrated that targeting specific pathways in parietal epithelial cells (PEC) can markedly alleviate experimental extracapillary glomerular injury [1]. Accumulating evidence has indicated the potential contributions of the mineralocorticoid receptor (MR) to the pathophysiology of chronic kidney disease. MR is expressed in endothelial cells, glomerular mesangial cells, podocytes, and distal tubular cells. Previous studies have shown that administering mineralocorticoid receptor antagonists has beneficial effects in various renal injury animal models, the role of the MR in extracapillary glomerulopathies is still elusive and mechanistically unclear. Methods To investigate the cell-specific role of the MR in PEC in the course of focal segmental glomerulosclerosis (FSGS) and crescentic glomerulonephritis (GN), we generated chimeric mice specifically lacking MR (Pec Cre Nr3c2lox/lox) in PECs using an inducible Cre recombinase system. Maladaptive FSGS was induced by combining a high-salt diet and deoxycorticosterone acetate (DOCA) with unilateral nephrectomy (DOCA-UniN). Crescentic glomerulonephritis (GN) was induced using the anti-glomerular basement membrane nephrotoxic serum (NTS) model. Results At baseline, Pec Cre Nr3c2wt/wt and Pec Cre Nr3c2lox/lox mice displayed no kidney morphology and function differences. When challenged by DOCA-UniN, PEC-selective Nr3c2 targeting significantly inhibited the expression of PEC activation markers Ki67, CD44, and FSGS lesions. Importantly, Pec Cre Nr3c2lox/lox mice showed less albuminuria and preserved renal function compared to Pec Cre Nr3c2 wt/wt counterparts. Likewise, Pec Cre Nr3c2lox/lox mice showed less albuminuria and preserved renal function in the NTS-induced CGN model. Crescents were also more numerous and organised in Pec Cre Nr3c2wt/wt mice than in Pec Cre Nr3c2lox/lox animals. Next, we examined whether pharmacological MR inhibition could alleviate the severity of crescentic GN. When Pec Cre Nr3c2wt/wt mice were orally given eplerenone for 14 days after the onset of the crescentic GN, they were significantly protected from renal injury and failure (decreased proteinuria, normal BUN and reduced number of crescent). Such global action was associated with less expression of the CD44 activation marker on PECs. Thus, genetic disruption of MR in PEC and pharmacological inhibition using eplerenone reduced glomerular expression of CD44 and crescent formation. Furthermore, kidney biopsies of individuals diagnosed with crescentic glomerulonephritis displayed increased expression of MR in PEC within FSGS and crescents. We next evaluated PEC migration under various conditions (DMSO, HB-EGF, Eplerenone, or HB-EGF+Eplerenone) for 24 hours. Eplerenone fully abrogated HB-EGF-induced PEC migration and Pcna, Snai1, and Vim mRNA expressions. Conclusion Altogether, these results indicate the critical role of MR in PEC activation during crescentic glomerulonephritis, along with the recently discovered CD9/EGFR/PDGFR [1] and CLDN1 pathways. This further supports the idea that the PEC phenotype switch is not a bystander event but plays a targetable critical active pathogenic role in FGSS and, more surprisingly, in crescentic GN. MR modulation using eplerenone may be a new therapeutic option for the management of such severe disease.

#1533 The relationship between the severity of anemia, the level of inflammation markers and the dose of epoetin in patients in pre-dialysis stages of CKD

Abstract Background and Aims Inflammation is known to be an important factor associated with hemoglobin variability in patients with anemia of chronic disease. However, the question remains whether high levels of C-reactive protein, a widely used marker of inflammatory activity, and other inflammatory markers predict less stable anemia control in patients with CKD. The purpose of this study was to establish the relationship between the severity of anemia with the levels of inflammatory markers (C-reactive protein, IL-6) and the dose of epoetin in patients with pre-dialysis stages of CKD. The purpose of our study was to study the age-related characteristics of the nutritional status in patients with CKD of the dialysis stages who are on parenteral nutrition. Method 180 patients (96 men and 84 women) with CKD as a result of nephropathies of diabetic and non-diabetic etiology were examined. Chronic pyelonephritis was diagnosed in 96 patients, chronic glomerulonephritis - in 73, polycystic kidney disease - in 11 patients. Glomerular filtration rate was calculated based on serum creatinine concentration using the CKD-EPI formula (2011). The patients were divided into 2 groups, depending on the achievement of the target hemoglobin value. Thus, group 1 included patients with CKD C3, C4, whose hemoglobin concentration was above 110 g/l (n = 101). Group 2 included patients whose hemoglobin concentration was less than 110 g/l in at least one analysis (n = 79). Results In the examined patients, a significant correlation was found between the range of hemoglobin concentration and the range of CRP concentration (p &amp;lt; 0.05), as well as between the range of hemoglobin concentration and the variation in the percentage of hypochromic erythrocytes (p &amp;lt; 0.05), between the range of hemoglobin concentration and the variation of ferritin ( p &amp;lt; 0.05). The change in the percentage of hypochromic erythrocytes also correlated with the change in IL-6 (p &amp;lt; 0.05) and the change in CRP ( p &amp;lt; 0.05). We found an association between the average weekly dose of epoetin and the levels of CRP, IL-6 and TNF-α. Patients with TNF-α levels ≥2 ng/mL and IL-6 ≥40 ng/mL required a significantly higher dose of epoetin than patients with lower levels of these markers (128 U/kg per week versus 57 U/kg at week). Conclusion The establishment of a relationship between inflammatory markers and hemogram and iron parameters suggests that inflammation had an indirect effect on the increase in hemoglobin through its effect on iron metabolism. The results of the study indicate the presence of diabetic and non-diabetic etiology of systemic inflammation in CKD, more so in the group of patients with type 2 diabetes mellitus.

Optimization of a bovine cytokine multiplex assay using a new bovine and cross-reactive equine monoclonal antibodies

Cytokines are important markers for immune activation, regulation, and homeostasis. The lack of monoclonal antibodies (mAbs) and sensitive assays to evaluate cytokine secretion has hindered research of bovine inflammation and immune regulation. We recently developed a fluorescent bead-based multiplex assay (multiplex assay) for bovine IL-10, TNF-α, and IFN-γ. Although the original assay covers a broad concentration range for the 3 targets, analytical sensitivity for IL-10 and IFN-γ could be improved to facilitate detection of these cytokines in their physiological low pg/mL range. To optimize the multiplex assay, we generated a new bovine IL-10 mAb and explored its use for the detection of intracellular and secreted bovine IL-10. The new bovine IL-10 mAb 130 recognized recombinant bovine IL-10 fusion protein and did not react with the fusion protein tag, or the TNF-α and IFN-γ standards in the multiplex assay. For improving IFN-γ detection, we explored cross-reactivity of anti-equine IFN-γ mAbs by intracellular staining of bovine stimulated peripheral blood mononuclear cells (PBMC). Equine IFN-γ mAb 3 showed excellent cross-reactivity with bovine IFN-γ by intracellular detection. Adding IL-10 mAb 130 and IFN-γ mAb 3 to the bovine multiplex assay substantially improved the analytical sensitivity with lower limits of detection in the low pg/mL range for all analytes. The detection ranges for the optimized multiplex assay were determined as 2 – 134,000 pg/mL for IL-10, 8 – 127,000 pg/mL for IFN-γ, and 12 – 193,000 pg/mL for TNF-α. The assay was next used to measure cytokine concentrations in cell culture supernatants from PBMC stimulated in plasma from whole blood stimulation to confirm native IL-10, TNF-α, and IFN-γ recognition and to explore the upper detection limits of the assay. In PBMC stimulation with a mix of phorbol myristate acetate (PMA) and ionomycin resulted in highest cytokine concentrations, while in plasma from whole blood stimulation, highest concentrations were observed in samples stimulated with a mix of lipopolysaccharide (LPS), phytohemagglutinin (PHA), and the TLR-2/6 agonist Pam2Csk4. PBMC and whole blood stimulation protocols showed that the optimized multiplex assay covers a wide linear detection range for measuring cytokine concentrations in bovine samples. For whole blood stimulation, a cocktail of pathogen associated molecular patterns elicited a stronger cytokine response than a mix of PMA and ionomycin, but response varied considerably between individual cattle. In conclusion, optimizing the bovine cytokine assay with new reagents improved the lower detection limits and widened the linear detection ranges while lowering the background of the multiplex assay.

#2684 Free light chains levels in ANCA associated vasculitis: a new potential inflammatory biomarker

Abstract Background and Aims Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a systemic disease characterized by an immune-mediated process where inflammation plays a central role. The widely available serum biomarkers of inflammation are not always able to detect ongoing disease activity in ANCA-associated vasculitis (AAV) patients. Free light chains (FLCs) expression levels have been proposed as new promising biomarker in some immune-mediated and inflammatory diseases. The aim of this study is to evaluate the expression levels of FLCs in patients affected by AAV and investigate the potential effect of rituximab treatment on FLCs levels. Method We conducted a retrospective multicenter study enrolling AAV patients in complete remission of AAV (defined as BVAS/GPA = 0); those with clinical suspicion of underlying hematologic malignancy were excluded. We analyzed κ and λ FLCs serum concentrations and evaluated their correlation with biomarkers of immune system activation, such as erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), serum immunoglobulin (Ig) levels, serum C3 and C4 complement and albumin levels (which has a negative correlation with acute inflammatory phase). We assessed impact of rituximab (RTX) therapy within the last 6 months on the same laboratory parameters. Results A total of 137 patients with AAV were recruited, who were gender balanced, had an average age of 68 years and an estimated glomerular filtration rate of 68 (43-89) mL/min/1.73 m2. Fifty-one patients received rituximab treatment (RTX group), while 86 patients were on other immunosuppressive maintenance therapies (non-RTX group). In comparison to non-RTX group, patients treated with RTX experienced higher complement C3 levels, lower ESR levels and lower FLCs κ (p = 0.063) and λ (p = 0.013) levels. The differences between RTX and non-RTX groups in terms of FLCs were even more prominent after correction to total Ig concentration (p = 0.004 for κ /Ig and p = 0.003 for λ /Ig, respectively). Both, serum free κ and λ levels were found to correlate significantly with ESR (R = 0.55 and p &amp;lt; 0.001 for κ; R = 0.53 and p &amp;lt; 0.001 for λ) and albumin (R = ‒0.38 and p &amp;lt; 0.001 for κ; R = ‒0.33 and p &amp;lt; 0.001 for λ). Additionally, serum free κ levels showed an inverse association with C3 (R = ‒0.18 and p = 0.041). Conclusion In subjects with AAV, FLC levels were found to be associated with markers of inflammation and complement activation; hence FLCs levels may represent a promising biomarker for detection of subclinical inflammation in AAV patients on maintenance therapy. Rituximab therapy showed a potential to reduce the levels of markers of subclinical inflammation, including FLCs.

#2101 Beyond corticosteroids: rituximab in managing minimal change disease and glucocorticoid-related toxicity

Abstract Background and Aims Minimal Change Disease (MCD) is the primary cause of Nephrotic Syndrome in children, accounting for 10 to 20% of cases in adults. Glucocorticoids (GC) remain the cornerstone of treatment. Despite a positive response in the majority of patients, up to 25% experience frequent relapses, and up to 30% are GC-dependent, exposing them to significant GC-related toxicity. Rituximab has been increasingly used in these patients, although 2021 KDIGO guidelines still points to cyclophosphamide as the preferred second-line therapy. This study aims to describe a single-centre experience with RTX, examining its effectiveness and assessing its potential to reduce GC exposure. Method A retrospective cohort study was conducted on 19 patients with MCD who were considered for RTX at adult age at a tertiary hospital centre between 2015 and 2023. Patients who refused treatment, those with MCD associated with other glomerular diseases, and those with less than 6 months of follow-up post-RTX were excluded from the study. Results Twelve patients met the inclusion criteria, including 5 diagnosed before the age of 18. The mean age at RTX initiation was 38.8 ± 14.8 years, with 75% being male. The median MCD duration pre-RTX was 140.5 [18.8–353.5] months, and the median follow-up post-RTX was 18.0 [12.5–41] months. All patients had preserved renal function and exhibited GC-dependency and/or frequent relapses, with 8 patients having received prior cyclophosphamide and/or cyclosporine A (CsA) treatment. At RTX initiation, all patients were on GC therapy (median 11.1 [10–50] mg/day), with 4 also on CsA. 10 patients were in complete remission, while 2 were in a relapse phase, subsequently achieving complete remission. Various induction regimens were employed: 6 patients received 1000 mg of RTX twice within 2 weeks, 1 received a single dose of 1000 mg, and 5 received a single dose of 500 mg. Out of the 12 patients, 5 did not receive RTX maintenance administrations, while 6 received 500 mg of RTX every 6 to 9 months and 1 patient received 1000 mg every 6 months. Only one adverse event was reported, one uncomplicated upper respiratory tract infection. Regardless of the induction regimen, all patients maintained a sustained response with complete remission for the following 6 months. All the 7 patients who underwent RTX maintenance did not experience disease relapse, although 2 continued GC therapy (one due to an associated autoimmune disease). Among the 5 patients who did not undergo RTX maintenance, 3 maintained complete remission throughout the follow-up, with a mean time free from any immunosuppression of 14.8 ± 10.6 months. The other 2 patients relapsed at a mean time of 27.5 ± 0.7 months. After relapse, 1 patient resumed GC therapy, and both started RTX maintenance with 500 mg every 6 to 9 months, subsequently achieving and maintaining complete remission. Among the 12 patients, 9 discontinued GC (1 continued CsA) after an average of 5.9 ± 4.2 months post-RTX, with a mean GC-free period of 16.6 ± 13.2 months during the follow-up period. Conclusion RTX proved to be safe and effective for steroid-dependent and/or frequently relapsing MCD, even with a low induction single dose of 500 mg. This low induction regimen may be an effective and potentially preferable option to minimize toxicity. RTX can significantly reduce relapse rate and steroid dose, avoiding complications associated with extended and high-dose GC administration. Notably, this outcome was not achieved previously with cyclophosphamide or CsA. RTX maintenance therapy may not be universally required for all patients with MCD, since a long period without relapse can be observed after induction therapy. Considering the current absence of a marker for disease activity, it should be taken into account individual patient characteristics and disease severity, particularly previous relapses after RTX induction. Considering the RTX effectiveness, ability to extend remission, safety, and GC sparing ability, it should be seriously considered as the preferred second-line treatment.

#1504 Performance evaluation of MicroVue sC5b-9 for analysis of urine samples

Abstract Background and Aims Complement mediated kidney diseases including C3 glomerulopathy (C3G), atypical uremic syndrome (aHUS), lupus nephritis (LN), and immunoglobulin A nephropathy (IgAN) are chronic inflammatory conditions characterized by dysregulated complement activation. Traditionally, complement activation is measured in plasma. However, patients with kidney disease often have an abundance of complement activation fragments in their urine—including soluble C5b-9 (sC5b-9), a marker of terminal pathway activation—highlighting the potential value of sC5b-9 measurement in urine for diagnosis and risk management in patients with C3G, aHUS, LN, IgAN, and other kidney diseases. Herein we evaluated the analytical performance of the Quidel MicroVue sC5b-9 Plus EIA for measurement of sC5b-9 in urine. Method The Quidel MicroVue sC5b-9 Plus EIA was evaluated using randomly collected healthy urine samples or healthy urine samples spiked with a known concentration of sC5b-9, as well as chronic kidney disease (CKD) urine samples. Results The analytical performance of the Quidel MicroVue sC5b-9 Plus EIA for measurement of sC5b-9 in urine met acceptability criteria for accuracy and precision. Assay accuracy was (100 ± 20%) and intra-assay precision as well as inter-assay precision was ≤ 11% coefficient of variability (CV). sC5b-9 was not detected in healthy urine samples (N = 40), but sC5b-9 was detected in a subset of urine samples from patients with CKD (N = 10). Positive linearity was observed over a wide range of concentrations. sC5b-9 measured in urine was not affected by hemoglobin or triglyceride, and was stable following three freeze-thaw cycles. Lastly, sC5b-9 measured in urine was stable when stored at −20°C and –80°C for 4 weeks. Long term stability testing at –80°C is underway. Conclusion Quidel MicroVue sC5b-9 Plus EIA is an accurate, reliable assay for detection of sC5b-9 in urine samples.

#2555 C4d—a novel predictor of the disease progression and treatment failure in primary focal segmental glomerulosclerosis?

Abstract Background and Aims Complement system seems to play a role in the pathogenesis of primary focal segmental glomerulosclerosis (pFSGS) where, due to unpredictable clinical course and outcome, novel prognostic factors are sought. The split product of C4 and tissue marker of complement activation, C4d, is a potential candidate whose prognostic significance was determined in this study. Method Patients &amp;gt;18 years with features consistent with pFSGS (full blown nephrotic syndrome, diffuse podocyte foot processes effacement and exclusion of known causes of FSGS), were recruited from our Hospital registry of kidney biopsies, from 2003 to 2021. Patients with end-stage renal disease (ESRD) defined as eGFR &amp;lt;15 ml/min/1.73 m2 were not included. Every renal biopsy specimen was analyzed by light, immunofluorescence and electron microscopy with additional immunochemistry for C4d performed on paraffin-embedded tissue using monoclonal rabbit antibody (detection system Ventana BenchMark Ultra). Samples with at least one non-globally sclerosed glomerulus (GSG) were examined by two renal pathologists who classified every non-GSG into C4d positive and negative. Based on ratio of C4d+ non-GGS/total N of non-GSG and C4d+ nonsclerotic glomeruli (NSG)/total N of NSG, patients were stratified into two groups: &amp;lt;50% and ≥50%. Primary outcome was defined as composite of ESRD and initial eGFR declining &amp;gt;50%. Failure to meet criteria for at least partial remission at the last follow-up visit according to KDIGO 2021 Guidelines was defined as treatment failure. Numeric variables are shown as median with interquartile range (IQR) and P value &amp;lt;0.05 was considered as significant. Results Relevant data of 58 included patients with renal outcomes are shown in Table. Median follow up was 90.7 (IQR 48-167) months. Patients with ≥50% of C4d+ non-GSG had higher proportion of treatment failure (Table) and worse renal survival (log-rank test, p = 0.006). In multivariate Cox regression analysis, after inclusion of age, sex, initial eGFR and 24-h proteinuria, IFTA, serum albumin and C4d category, only C4d ≥50% (HR = 4.077, 95% CI 1.101-15.09, p = 0.035) and IFTA (HR = 1.052, 95% CI 1.019-1.085, p = 0.002) remained independent predictors of progression to defined endpoint. Likewise, patients with ≥50% of C4d+ NSG/total N of NSG had higher proportion of treatment failure (chi-square, p = 0.03) and worse renal survival (log-rank, p = 0.037). Conclusion C4d deposition is an independent predictor of disease progression, treatment failure and renal survival in pFSGS. Significant influence of NSG-C4d deposition on disease progression may indicate pathophysiological role of the complement system activation in pFSGS independently of the presence of glomerular sclerosis.

#435 Endothelial activation and inflammation in chronic kidney disease (CKD): role of neutrophil extracellular traps (NETs)

Abstract Background and Aims Advanced chronic kidney disease (CKD), especially in stages 4-5, amplifies cardiovascular disease (CVD) risk by around 50%. This heightened susceptibility is linked to a 1.5 to 3-fold increase in venous thromboembolism incidence, driven by coagulation dysregulation and heightened inflammation. During inflammation, neutrophils can release extracellular traps (NETs), that was described contribute to endothelial damage, through adhesion molecule elevation, and tissue factor (TF) secretion, exacerbating thrombosis. Additionally, NETs interact with von Willebrand Factor (vWF) and factor XII, further amplifying thrombus formation and the activation of the intrinsic coagulation pathway. The aim of this study was to observe whether NETs may contribute to increased CVD risk in CKD patients by inducing endothelial activation and thromboinflammatory responses to a larger extent compared to NETs from healthy donors. Method For that, neutrophils were isolated from healthy donors’ and CKD patients’ (stages 3-5 HD) peripheral blood, and NETs were collected by stimulating neutrophils with PMA for 3.5 hours. Human aortic endothelial cells (HAoECs) were subsequently exposed to NETs for 3 to 24 hours, followed by gene expression analysis with a focus on inflammation, endothelial activation, and prothrombotic markers. Additionally, protein analysis of the supernatant was conducted using ELISA. All experiments were performed under ethical protocol EK 225-21 from the University Hospital of Aachen. Results Exposure to both healthy NETs as well as the ones isolated from CKD patients resulted in a notable upregulation of endothelial activation (VCAM-1), prothrombotic (TF), and inflammatory (IL-6) gene expression within 3 hours, without difference between healthy and CKD conditions. On the other hand, when examining the cellular supernatant, a significantly higher increase in vWF secretion was observed upon treatment with CKD-NETs compared to healthy NETs. Furthermore, while secretion of the inflammatory cytokine IL-6 presented a comparable increase upon treatment with NETs derived from healthy and CKD neutrophils, IL-1β secretion was markedly enhanced after CKD-NET treatment in comparison to healthy NETs. Conclusion In summary, our findings suggest that NETs exert a significant influence on endothelial cells, contributing to increased thromboinflammatory activation. Notably, CKD-NETs evoked a more rapid impact on the endothelium, accompanied by increased secretion of IL-1β and vWF, and underlying mechanisms will be further investigated.

#933 Serum and kidney complement and severity of ANCA associated vasculitis in the kidney

Abstract Background and Aims Kidney involvement in ANCA associated vasculitis (AAV) is commonly described as pauci-immune based on histological characteristics. However, we now know that the complement system is activated and contributes to the pathogenesis of AAV – with Avacopan (C5a inhibitor) demonstrating superior efficacy in maintenance of remission over Prednisolone in the ADVOCATE trial. Our aim was to evaluate if there is an association between kidney disease severity and the presence of serum and histological complement activation markers. Method Retrospective cohort study of 59 patients with AAV diagnosed between November 2015 and May 2019. Complement activation markers were serum complements (C3 and C4) levels and presence of complement (C3, C1q and C4) in glomerular capillary walls in immunofluorescence with intensity of 2+ and 3+. Kidney disease severity markers were peak serum creatinine value at presentation, anti-MPO or anti-PR3 levels, and number and proportion of glomeruli with crescents on kidney biopsy. Associations were evaluated using Spearman correlation or Mann Whitney U test as appropriate Results Among 59 patients with biopsy-proven AAV in the kidney, the median (25th percentile, 75th percentile) age was 68.8 (60.7, 73.4) years, serum creatinine was 263 (156, 560) µmol/L, and anti-MPO and anti-PR3 levels were 100.0 (81.5, 199.2) and 128.8 (22.9, 200) in 41 and 7 patients, respectively. respectively. The number and proportion of glomeruli with crescents were 6 (3, 12) and 33.3% (12.0%, 42.6%), respectively. Serum C3 and C4 were performed in 41 patients and the median levels were 1.00 (0.83, 1.14) and 0.24 (0.18, 0.31), respectively. Serum C3 level did not correlate with serum creatinine, anti-MPO or anti-PR3 titers, and number and proportion of glomeruli with crescents. Serum C4 level was negatively correlated with anti-MPO titer (34 patients; r = −0.393, p = 0.02) but did not correlate with serum creatinine or number or proportion of crescents. Complement in the glomerular capillary wall was present in 8 patients (13.6%): C3, C1q and C4 were present in 8, 3 and 1 patients, respectively. Serum creatinine [median 299 (IQR 133, 998) µmol/L versus 261 (156, 359) µmol/L, p = 0.39], anti-MPO titer [100 (88.3, 200) IU/ml versus 100 (79.4, 198) IU/ml, p = 0.74], number of crescents [14 (4, 21) versus 5 (3, 12), p = 0.90] and proportion of crescents [38.9% (12.5%, 42.3%) versus 31.3% (11.1%, 44.3%), p = 0.59] were not different in those with and without complement in the kidney biopsy. Conclusion The presence of complement activation markers was not associated with kidney disease severity in AAV. However, the detection of clinically significant associations may have been limited by our cohort size.

#2191 Platelet function in chronic kidney disease; can flow cytometry guide in the difficult balance between risk for bleeding versus thrombotic events?

Abstract Background and Aims Increased risk of bleeding is a well-known complication of chronic kidney disease (CKD). However, these patients also have an increased risk of thrombotic events. Several studies have implicated both impaired and enhanced platelet function in patients with chronic kidney disease, but results vary between different studies and methods. Flow cytometry has emerged as a new method to study platelet function. Our aim was to investigate platelet function using flow cytometry in patients with chronic kidney disease. Method 20 patients were included between February and May 2023. Pre-dialytic patients with an eGFR between 8-20 mL/min/1,73 m2 were included, mean eGFR 14.7 mL/min/1,73 m2. Patients with platelet levels &amp;gt;100 × 109/L were included. Medication in the form of anticoagulants, NSAIDs, platelet inhibitors or SSRIs were used as exclusion criteria. Platelet activation assay was performed with flow cytometry. The expression of activation markers PAC-1 (activated GPIIb/IIIa), CD62P (P-selectin) and CD63 (dense granules) were analysed before and after activation with ADP, CRP-XL (collagen stimulating peptide, activates GPVI) or TRAP-6 (stimulates platelet activating receptor 1, PAR1). Platelets from 20 healthy control subjects were analysed for comparison. Results The level and size of platelets (MPV) were comparable in both groups. There were significantly higher levels of D-dimer in the CKD group vs healthy controls (1,17 mg/L FEU vs 0,27 mg/L FEU). Except for the decreased expression of activated GPIIb-IIIa receptor after activation with ADP and CRP-XL in one patient, the platelet activation did not significantly differ between CKD patients and healthy controls. Conclusion No significant differences in the activation of platelets were observed between the CKD population and the healthy controls when analysed by flow cytometry. Elevated levels of D-dimer in CKD patients have previously been described and are believed to be due to increased fibrin formation, lysis and decreased renal clearance. Further studies in a larger patient population, including thrombocytopenic patients are planned, with greater focus to be placed on dense granula quantities which may correlate with decreased levels in the CKD population.

Inflammatory activity evaluation in patients with axial spondyloarthritis using MRI relaxometry and mucosal-associated invariant T cells.

Currently, there is a lack of an objective quantitative measure to comprehensively evaluate the inflammatory activity of axSpA, which poses certain challenges in accurately assessing the disease activity. To explore the value of combined-parameter models of sacroiliacjoints (SIJs) MRI relaxometry and peripheral blood Mucosal-associated invariant T (MAIT) cells in evaluating the inflammatory activity of axial spondyloarthritis (axSpA). This retrospective clinical study included 88 axSpA patients (median age 31.0 (22.0, 41.8) years, 21.6% females) and 20 controls (median age 28.0 (20.5, 49.5) years, 40.0% females). The axSpA group was classified into active subgroup (n=50) and inactive subgroup (n=38) based on ASDAS-CRP. All participants underwent SIJs MRI examination including T1 and T2* mapping, and peripheral blood flow cytometry analysis of MAIT cells (defined as CD3+Vα7.2+CD161+) and their activation markers (CD69). The T1 and T2* values, as were the percentages of MAIT cells and CD69+MAIT cells were compared between different groups. Combined-parameter models were established using logistic regression, and ROC curves were employed to evaluate the diagnostic efficacy. The T1 values of SIJs and %CD69+MAIT cells in the axSpA group and its subgroup were higher than the control group (p<0.05), while %MAIT cells were lower than the control group (p<0.05). The T1 values and %CD69+MAIT cells correlated positively, while %MAIT cells correlated negatively, with the ASDAS-CRP (r=0.555, 0.524, -0.357, p<0.001). Between the control and axSpA groups, and between the inactive and active subgroups, the combined-parameter model T1 mapping+%CD69+MAIT cells has the best efficacy (AUC=0.959, 0.879, sensibility=88.6, 70%, specificity=95.0, 94.7%, respectively). The combined-parameter model T1 mapping+%CD69+MAIT cells allows a more accurate evaluation of the level of inflammatory activity.