Immune Complex Formation Research Articles

Renal Injury During Viral Infections

Renal pathologies following viral infections have become an emerging public health problem in both developed and developing countries. Diagnostic criteria are complex. In most cases, they involve correlation between clinical, biological and histological data, with occasional recourse to molecular biology techniques. Several mechanisms are involved in the pathogenesis of virus-related nephropathy, including virus tropism in the kidney, formation of immune complexes in situ or in the bloodstream, direct cytopathogenic effects, and multiple organ failure. The hepatitis C virus is responsible for three main types of kidney disease: membranoproliferative glomerulnephritis, cryoglobulinemia and membranous nephropathy. Hepatitis B virus is associated with membranous nephropathy, membranoproliferative glomerulnethritis, and IgA nephropathy. HIV (human immunodeficiency virus) infection is associated with several glomerular and tubular kidney damage. HIVAN (HIV-associated nephropathy), a specific entity mainly affecting Africans and African-Americans, presents as a rapidly progressive glomerulonephritis rapidly progressing to the terminal stage. Infections secondary to adenovirus, cytomegalovirus, epstein-barr virus, poliomavirus and coronavirus are often responsible for acute or chronic tubulointerstitial nephritis. Treatment is mainly symptomatic, based on nephroprotection measures, rarely combined with antiviral therapy. Prophylaxis with vacci-nation, when available, remains the best means of preventing viral nephropathy.

The role of BAFF and APRIL in IgA nephropathy: pathogenic mechanisms and targeted therapies.

Immunoglobulin A nephropathy (IgAN), characterized by mesangial deposition of galactose-deficient-IgA1 (Gd-IgA1), is the most common biopsy-proven primary glomerulonephritis worldwide. Recently, an improved understanding of its underlying pathogenesis and the substantial risk of progression to kidney failure has emerged. The "four-hit hypothesis" of IgAN pathogenesis outlines a process that begins with elevated circulating levels of Gd-IgA1 that trigger autoantibody production. This results in the formation and deposition of immune complexes in the mesangium, leading to inflammation and kidney injury. Key mediators of the production of Gd-IgA1 and its corresponding autoantibodies are B-cell activating factor (BAFF), and A proliferation-inducing ligand (APRIL), each playing essential roles in the survival and maintenance of B cells and humoral immunity. Elevated serum levels of both BAFF and APRIL are observed in patients with IgAN and correlate with disease severity. This review explores the complex pathogenesis of IgAN, highlighting the pivotal roles of BAFF and APRIL in the interplay between mucosal hyper-responsiveness, B-cell activation, and the consequent overproduction of Gd-IgA1 and its autoantibodies that are key features in this disease. Finally, the potential therapeutic benefits of inhibiting BAFF and APRIL in IgAN, and a summary of recent clinical trial data, will be discussed.

Ultrasensitive Detection of PSA Using Antibodies in Crowding Polyelectrolyte Multilayers on a Silicon Nanowire Field-Effect Transistor.

Immunosensors based on field-effect transistors with nanowire channels (NWFETs) provide fast and real-time detection of a variety of biomarkers without the need for additional labels. The key feature of the developed immunosensor is the coating of silicon NWs with multilayers of polyelectrolytes (polyethylenimine (PEI) and polystyrene sulfonate (PSS)). By causing a macromolecular crowding effect, it ensures the "soft fixation" of the antibodies into the 3-D matrix of the oppositely charged layers. We investigated the interaction of prostate-specific antigen (PSA), a biomarker of prostate cancer, and antibodies adsorbed in the PEI and PSS matrix. In order to visualize the formation of immune complexes between polyelectrolyte layers using SEM and AFM techniques, we employed a second clone of antibodies labeled with gold nanoparticles. PSA was able to penetrate the matrix and concentrate close to the surface layer, which is crucial for its detection on the nanowires. Additionally, this provides the optimal orientation of the antibodies' active centers for interacting with the antigen and improves their mobility. NWFETs were fabricated from SOI material using high-resolution e-beam lithography, thin film vacuum deposition, and reactive-ion etching processes. The immunosensor was characterized by a high sensitivity to pH (71 mV/pH) and an ultra-low limit of detection (LOD) of 0.04 fg/mL for PSA. The response of the immunosensor takes less than a minute, and the measurement is carried out in real time. This approach seems promising for further investigation of its applicability for early screening of prostate cancer and POC systems.

P264 The utility of ANCA in Ulcerative Colitis and Crohn’s Disease: A Retrospective Cohort Study in Taiwan

Abstract Background Inflammatory bowel disease (IBD) includes two chronic idiopathic inflammatory diseases: ulcerative colitis (UC) and Crohn disease (CD). The diagnosis of IBD depends on clinical, endoscopic, histological, radiological and biochemical criteria, which may be invasive, time consuming and usually not accepted by patients with IBD. Antineutrophil cytoplasmic antibodies (ANCAs) is believed to be related to IBD. The aim of this study was to investigate these serological markers and the evidence for their use in the diagnosis and management of IBD in Taiwan. Methods We conducted a retrospective cohort study in adult IBD patients who had received the serum examinations using the medical records of China Medical University Hospital between 1 January 1980 and 31 October. 2023. Results A total of 301 IBD patients (194 with UC, 107 with CD) were included in this current study. A high proportion were male (IBD 70.41%; UC 65.63%, and CD 76.71%). The mean diagnostic age of these enrolled patients was 42.9 years. In our patients, the prevalence of positive anti-HCV Ab is 0.0% in UC patients and 0.96% in CD patients. However, the prevalence of positive HBsAg was 14.5% in UC patients and 9.4% in CD patients. The prevalence of pANCA was 21.2% in UC patients and 1.4% in CD patients, respectively. The prevalence of cANCA was 3.1% in UC patients and 0.0% in CD patients. This pattern of low sensitivity and high specificity for pANCA is also seen in UC patients in various cohort studies. The serum positivity of p-ANCA was significantly higher in UC patients (Figure 1). UC patients with positive p-ANCA were older than CD patients with positive p-ANCA (44.9 vs. 37.3 years). Furthermore, we found that the incidence of positive p-ANCA in UC patients with E1, E2, and E3 at diagnosis was 3.5%, 39.2%, and 57.1%, respectively (Table 1). The serum levels of ANCA-IgG were indeed higher in patients in the severe group than those in the moderate and mild groups. Conclusion Serological biomarkers have been demonstrated to be a series of rapid, non-invasive approaches for assessments of early diagnosis, disease activity and prognosis for IBD. ANCA may be helpful in the early diagnosis of UC and in differentiating it from CD. UC patients with positive ANCA have a higher rate of intestinal mucosal vasculitis than UC patients with negative ANCA. Furthermore, ANCA may also contributes to the pathogenesis of HBV-related systemic vasculitis. Therefore, the management of HBV-related vasculitis includes control the immune complex formation and reaction as well as antiviral agents to reduce the antigenic load resulting in reduction of inflammation. Moreover, effective biomarkers with high sensitivity and specificity need to be investigated in the future.

ImmunoglobulinA vasculitis

The immune-mediated small vessel vasculitis is known as Schoenlein-Henoch purpura predominantly from pediatrics and in these cases occurs more frequently after infections of the upper airways. In adults, immunoglobulinA (IgA) vasculitis often proceeds more severely und recurrently with the classical tetrad of skin manifestations in the sense of leukocytoclastic vasculitis, joint affection, gastrointestinal involvement and IgA nephritis, in contrast to the mostly mild and self-limiting course in children. The background of this systemic vasculitis with formation of IgA immune complexes is considered to be an altered glycosylation of IgA, as this causes the exposure of binding sites for autoantibodies so that an immune complex reaction can be elicited. This ultimately leads to perivascular deposition of IgA and afurther activation of neutrophils. Groundbreaking in the diagnostics is the histological detection of leukocytoclastic vasculitis and in cases of renal manifestations akidney biopsy with characteristic deposits of immune complexes, which cannot be clearly differentiated from IgA nephropathy. The treatment is aimed at the respective manifestation and is mostly based on consensus recommendations due to the lack of randomized studies. In addition to immunosuppressive medication, in the presence of achronic kidney disease general nephroprotection is becoming increasingly more important also by inhibition of sodium-glucose transporter2 (SGLT2). The type and extent of kidney involvement and also rare cardiac manifestations are the main determinants of the prognosis. Continuous medical accompaniment of those affected is necessary due to the possible progression of the disease and the risk of recurrence.

Heat Treatment Augments Antigen Detection of Dirofilaria immitis in Apparently Healthy Companion Dogs (3.8% to 7.3%): Insights from a Large-Scale Nationwide Survey across the United States.

Heartworm disease (HWD) is a vector-borne disease caused by the filarial nematode Dirofilaria immitis. Low antigen levels caused by immune complex formation preclude HWD diagnosis. Heat treatment is an immune complex dissociation technique used to enhance antigen detection. Only a few studies have reported the benefits of heat treatment in nationwide surveys. To investigate the impact of heat treatment on the seroprevalence of HWD in companion dogs in the USA, serum samples (n = 3253) were analyzed for D. immitis antigen (DiroCHEK®, Zoetis) without and with heat treatment of the samples. Compared to sera without heat treatment, heat treatment significantly increased overall prevalence from 3.8% (123/3253) to 7.3% (237/3253) (p < 10-4), expanding antigen detection from 32 to 39 of the 48 states and Washington District of Columbia included in this study. This study represents the largest nationwide survey of HW antigen detection in dogs in the US applying heat treatment to canine sera. The heat treatment used herein has the advantage of requiring a low volume of serum, making it optimal for use in routine diagnosis. Heat treatment should be used routinely by reference laboratories and veterinary clinics in patients with a negative initial test.

Progress of rituximab in the treatment of systemic lupus erythematosus and lupus nephritis.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with heterogeneous clinical manifestations, often leading to significant morbidity and mortality, particularly due to lupus nephritis (LN). The standard therapeutic approach involving mycophenolate mofetil, cyclophosphamide, and glucocorticoids has shown limitations due to cumulative toxicity and side effects. The introduction of biologic agents, especially rituximab (RTX), a chimeric monoclonal antibody targeting CD20+ B cells, has revolutionized the treatment landscape. This review synthesized the current understanding of B cells' role in SLE and LN and evaluates RTX's therapeutic impact. B cells contribute to disease pathogenesis through autoantibody production and immune complex formation, leading to tissue damage. RTX's mechanisms of action, including Complement-Dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), and induction of apoptosis, have demonstrated efficacy in both SLE and LN treatment. Clinical studies have reported remission rates and improved renal outcomes with RTX use, although challenges such as human anti-chimeric antibody development and optimal dosing persist. The review emphasized the need for continued research to elucidate RTX's long-term benefits and risks, and to explore personalized treatment strategies that incorporate B cell biology for better disease management in SLE and LN.

Transient receptor potential vanilloid 1 interacts with Toll-like receptor 4 (TLR4)/cluster of differentiation 14 (CD14) signaling pathway in lipopolysaccharide-mediated inflammation in macrophages.

Transient receptor potential vanilloid 1 (TRPV1), a ligand-gated cation channel, is a receptor for vanilloids on sensory neurons and is also activated by capsaicin, heat, protons, arachidonic acid metabolites, and inflammatory mediators on neuronal or non-neuronal cells. However, the role of the TRPV1 receptor in pro-inflammatory cytokine secretion and its potential regulatory mechanisms in lipopolysaccharide (LPS)-induced inflammation has yet to be entirely understood. To investigate the role and regulatory mechanism of the TRPV1 receptor in regulating LPS-induced inflammatory responses, bone marrow-derived macrophages (BMDMs) harvested from wild-type (WT) and TRPV1 deficient (Trpv1-/-) mice were used as the cell model. In WT BMDMs, LPS induced an increase in the levels of tumor necrosis factor-α, IL-1β, inducible nitric oxide synthase, and nitric oxide, which were attenuated in Trpv1-/- BMDMs. Additionally, the phosphorylation of inhibitor of nuclear factor kappa-Bα and mitogen-activated protein kinases, as well as the translocation of nuclear factor kappa-B and activator protein 1, were all decreased in LPS-treated Trpv1-/- BMDMs. Immunoprecipitation assay revealed that LPS treatment increased the formation of TRPV1-Toll-like receptor 4 (TLR4)-cluster of differentiation 14 (CD14) complex in WT BMDMs. Genetic deletion of TRPV1 in BMDMs impaired the LPS-triggered immune-complex formation of TLR4, myeloid differentiation protein 88, and interleukin-1 receptor-associated kinase, all of which are essential regulators in LPS-induced activation of the TLR4 signaling pathway. Moreover, genetic deletion of TRPV1 prevented the LPS-induced lethality and pro-inflammatory production in mice. In conclusion, the TRPV1 receptor may positively regulate the LPS-mediated inflammatory responses in macrophages by increasing the interaction with the TLR4-CD14 complex and activating the downstream signaling cascade.

ADAMTS-13 conformation influences autoimmune recognition in immune thrombotic thrombocytopenic purpura

BackgroundPatients with immune-mediated thrombotic thrombocytopenic purpura (iTTP) have anti–ADAMTS-13 immunoglobulin G (IgG) autoantibodies that enhance ADAMTS-13 clearance and/or inhibit its function. ADAMTS-13 normally circulates in a closed conformation, which is manifested by the interaction of the CUB domains with the central spacer domain. Disruption of the spacer–CUB interaction opens ADAMTS-13, which augments its proteolytic function but may also expose cryptic autoimmune epitopes that promote further autoantibody recognition. ObjectivesTo explore differences in autoantibody binding to ADAMTS-13 in its closed or open conformations in patients with iTTP and to correlate these differences with disease-related parameters. MethodsWe developed a novel assay to measure autoantibodies binding to closed and open ADAMTS-13. Autoantibody titer and IgG subclass binding to open or closed ADAMTS-13 were measured in 70 iTTP first presentation samples and correlated with clinical data, remission, and relapse. ResultsIn 70 patients with iTTP, the mean autoantibody titer against open ADAMTS-13 was, on average, approximately 2-fold greater than that against closed ADAMTS-13, suggesting that ADAMTS-13 opening increases epitope exposure and immune complex formation. Autoantibody titer against closed/open ADAMTS-13 and IgG subclass did not correlate with ADAMTS-13 antigen at presentation. Two patients with iTTP and persistent autoantibodies lost specificity for closed ADAMTS-13 in remission. Recognition of closed/open ADAMTS-13 and autoantibody IgG subclass between the first and second iTTP episodes were very similar. ConclusionADAMTS-13 autoantibody binding is highly influenced by ADAMTS-13 conformation. Although this does not appear to modify the pathogenicity of autoantibodies, the autoantibody signature at relapse suggests that relapse represents re-emergence of the original autoimmune response rather than de novo presentation.

The contribution of a proliferation-inducing ligand (APRIL) and other TNF superfamily members in pathogenesis and progression of IgA nephropathy.

Advances in our understanding of the pathogenesis of immunoglobulin A nephropathy (IgAN) have led to the identification of novel therapeutic targets and potential disease-specific treatments. Specifically, a proliferation-inducing ligand (APRIL) has been implicated in the pathogenesis of IgAN, mediating B-cell dysregulation and overproduction of pathogenic galactose-deficient IgA1 (Gd-IgA1). Animal and clinical studies support the involvement of APRIL in the pathogenesis and progression of IgAN. An elevated level of APRIL is found in IgAN when compared with controls, which correlates with the level of Gd-IgA1 and associates with more severe disease presentation and worse outcomes. Conversely, anti-APRIL therapy reduces pathogenic Gd-IgA1 and IgA immune complex formation and ameliorates the severity of kidney inflammation and injury. Genome-wide association studies in IgAN have identified TNFSF13 and TNFRSF13B, a cytokine ligand-receptor gene pair encoding APRIL and its receptor, respectively, as risk susceptibility loci in IgAN, further supporting the causal role of the APRIL signalling pathway in IgAN. Several novel experimental agents targeting APRIL, including atacicept, telitacicept, zigakibart and sibeprenlimab, are currently under investigation as potential therapies in IgAN. Preliminary results suggest that these agents are well-tolerated, and reduce levels of Gd-IgA1, with corresponding improvement in proteinuria. Further studies are ongoing to confirm the safety and efficacy of anti-APRIL approaches as an effective therapeutic strategy in IgAN.

IgA nephropathy.

IgA nephropathy (IgAN), the most prevalent primary glomerulonephritis worldwide, carries a considerable lifetime risk of kidney failure. Clinical manifestations of IgAN vary from asymptomatic with microscopic or intermittent macroscopic haematuria and stable kidney function to rapidly progressive glomerulonephritis. IgAN has been proposed to develop through a 'four-hit' process, commencing with overproduction and increased systemic presence of poorly O-glycosylated galactose-deficient IgA1 (Gd-IgA1), followed by recognition of Gd-IgA1 by antiglycan autoantibodies, aggregation of Gd-IgA1 and formation of polymeric IgA1 immune complexes and, lastly, deposition of these immune complexes in the glomerular mesangium, leading to kidney inflammation and scarring. IgAN can only be diagnosed by kidney biopsy. Extensive, optimized supportive care is the mainstay of therapy for patients with IgAN. For those at high risk of disease progression, the 2021 KDIGO Clinical Practice Guideline suggests considering a 6-month course of systemic corticosteroid therapy; however, the efficacy of systemic steroid treatment is under debate and serious adverse effects are common. Advances in understanding the pathophysiology of IgAN have led to clinical trials of novel targeted therapies with acceptable safety profiles, including SGLT2 inhibitors, endothelin receptor blockers, targeted-release budesonide, B cell proliferation and differentiation inhibitors, as well as blockade of complement components.

Evaluation of Complement Level, Serum Electrophoretic Panel, and Anti-glomerular Basement Membrane in Coronavirus Disease 2019: Focus on Likelihood of Hypersensitivity Type III

&lt;strong data-sider-select-id="e0ba6517-9e2c-4620-8827-36ac66373c0f"&gt;Background: As an inflammatory process, the emergence of autoimmunity in COVID-19 is likely through molecular mimicry. In autoimmune hypersensitivity-III, immune complex (IC) formation leads to complement activation, inflammation amplification, and tissue damage. Having accumulated IC, lesions in organs such as the lung with tiny vessels are formed, and the complement is depleted. As a systemic disease, COVID-19 has similar therapies and laboratory findings with hypersensitivity-III. &lt;strong data-sider-select-id="09e60b77-93f6-4c2f-b1e8-fa341b0790ee"&gt;Objectives: This study was designed to evaluate complement level, serum electrophoretic pattern, and anti-glomerular basement membrane (GBM) in COVID-19 patients. &lt;strong data-sider-select-id="55fd5e75-5740-416a-8241-47d724fa5d6c"&gt;Materials and Methods: Blood was collected, and complement component 3 (C3), C4, 50% hemolytic complement (CH50), anti-GBM level, as well as serum electrophoresis were evaluated. &lt;strong data-sider-select-id="5792ee88-f1ad-4772-83e6-41da9ca0927f"&gt;Results: C3/C4 levels were normal in 70% and increased in 30% of the subjects. Albumin was normal in 76.67% and decreased in 23.33% of the patients. Furthermore, alpha-1 and alpha-2 were normal in 33.33% and 53.33% of the patients, but their levels increased in 66.67% and 46.67% of patients, respectively. Moreover, gamma-band was normal in 70% and increased in 30% of the participants. Additionally, all of the subjects had normal beta-band, CH50, and anti-GBM. &lt;strong data-sider-select-id="5b52d788-9f72-4772-b070-52de86d41206"&gt;Conclusion: The possibility of autoimmune hypersensitivity-III in the lung and kidneys is not understood. Furthermore, alpha band may be a candidate red flag showing changes from moderate to severe forms of the disease.

Incidence and Predictive Factors of Heparin-Induced Thrombocytopenia: A Comprehensive Analysis Using National Inpatient Data

Introduction: Heparin-induced thrombocytopenia (HIT) is a serious complication associated with heparin therapy, characterized by an immune reaction involving antibodies against heparin-platelet factor 4 (PF4). This immune complex formation triggers platelet activation, blood clotting, and reduced platelet counts. Several factors, including previous heparin exposure, duration of exposure, and certain comorbidities, have been examined as potential risk factors for HIT development. In this study, our objective was to determine the incidence of HIT and identify predictive factors associated with its occurrence. Methods: We conducted an analysis using the National Inpatient Sample (NIS) data from 2020 to investigate the incidence of HIT during that year and its correlation with specific comorbidities. Patient identification was based on the International Classification of Diseases (ICD-10) code D75.82. The incidence and associated comorbidities were evaluated using multivariate logistic analysis with Stata 17. Results: Among the 32,355,827 adult patients admitted throughout the United States in 2020, a total of 11,380 cases of HIT were identified. The incidence of HIT was significantly higher in male patients, obese individuals, those with acute kidney injury (AKI), chronic kidney disease (CKD), type II diabetes mellitus (DMII), heart failure (HF), primary hypercoagulable states, and autoimmune diseases such as systemic lupus erythematosus (SLE). The highest risk of developing HIT was observed in patients with thrombophilia (OR 4.17, 95% CI 3.66-4.75, P = .000), AKI (OR 3.53, 95% CI 3.19-3.91, P = .000), and HF (OR 2.10, 95% CI 1.90-2.33, P = .000). Among autoimmune diseases studied, only SLE was associated with an increased odds ratio for developing HIT (OR 1.60, 95% CI 1.06-2.41, P = .026). Conclusion: The incidence of HIT varies and is influenced by the presence of specific comorbidities. Further studies are recommended to investigate additional factors that may increase the likelihood of HIT development. This information could aid in validating and implementing standard precautionary measures in patients at higher risk of developing HIT.

249. SARS-CoV-2 Spike Immune Complexes Induce NETosis in COVID-19

Abstract Background Disease severity in SARS-CoV-2 infection is associated with elevated levels of neutrophil extracellular traps (NETs) and antibodies. We previously demonstrated that plasma from patients with SARS-CoV-2 infection stimulates the release of NETs by healthy donor neutrophils and that this can be reversed by R406, a spleen tyrosine kinase (SYK) inhibitor. Immune complexes, stimulating through Fc receptors, induce robust NETosis through a SYK-mediated pathway. Therefore, we hypothesized that SARS-CoV-2 spike immune complexes can mediate the release of NETs from neutrophils and that this process can be reversed by R406. Methods To test this, we created spike specific immune complexes utilizing an optimized concentration of affixed spike-trimer and SARS-CoV-2 patient plasma and evaluated the ability of these complexes to stimulate NETosis from healthy neutrophils. We quantified both IgG and IgA spike specific immune complex formation by ELISA utilizing HRP conjugated secondary antibodies (Promega Glomax Plate Reader). Healthy donor neutrophils were isolated, added to wells containing the spike immune complexes with and without R406, and live cell imaging (Incucyte S3) was used to visualize and quantify NETs. Results Incubation of COVID-19 patient plasma with spike protein resulted in an average 7-fold and 9-fold increase in the formation of IgA and IgG spike specific immune complexes, respectively, compared to spike alone (Figure 1A). After stimulating healthy donor neutrophils with the spike immune complexes created from six SARS-CoV-2 patient plasma samples, we observed a mean 200% increase in the induction of NETs relative to spike alone (Figure 1B). There were positive correlations between immune complexes formation and NETs formed in cells exposed to those wells (IgA R2= 0.67, p=0.01 and IgG R2= 0.82, p=0.002). Preliminary data suggests that spike-immune complex NET formation can be reduced by R406 (n=3 COVID-19 plasma donors). Figure 1A-B A) Quantification of IgA and IgG spike immune complexes was measured through measurement of absorbance at 405 nm after exposure to ABTS for 15 minutes. Value normalized to the spike alone condition ran on each day, and data represents a fold change from that condition (Ordinary One-way ANOVA: ** indicates p &amp;lt; 0.01; *** indicates p &amp;lt; 0.001; **** indicates p &amp;lt;0.0001). B) Induction of NETs 6 hours after exposure, demonstrating percent increase in NETosis in plasma isolated from COVID-19 patients (n=6) and healthy patients (n=2) in the presence and absence of SARS-CoV-2 spike immune complexes. Area of NETs was quantified by calculating the area (µm2 ) of ecDNA, visualized by Incucyte® Cytotox Green Dye. Area of NETs at T0 was subtracted from all conditions, and the induction of NETs was calculated as percentage increase relative to NETosis induced by SARS-CoV spike alone condition run on each day (Ordinary One-way ANOVA: ** indicates p &amp;lt; 0.01; *** indicates p &amp;lt; 0.001; **** indicates p &amp;lt;0.0001). Conclusion Using our ELISA, we demonstrated that we can reliably generate spike-specific IgG and IgA immune complexes. Stimulation of healthy donor neutrophils by spike immune complexes increased NET-formation compared to spike alone providing evidence of immune complex mediated NET induction in SARS-CoV-2 infection. Disclosures All Authors: No reported disclosures

Treatment with a tissue-selective oestrogen complex does not affect disease pathology but reduces pre-BI cells in lupus-prone mice

Objective Systemic lupus erythematosus (SLE or lupus) is an autoimmune disease characterized by B-cell dysfunction, production of autoantibodies, and immune complex formation. Lupus is overrepresented in females, indicating that sex hormones play a role in the pathophysiology. Treatment with a tissue-selective oestrogen complex (TSEC) containing conjugated oestrogens and the selective oestrogen receptor modulator bazedoxifene (BZA) protects against postmenopausal vasomotor symptoms and osteoporosis, but its impact on organ damage in lupus is not fully understood. Method We used ovariectomized MRL/lpr mice, treated with two different physiological doses of 17β-oestradiol-3-benzoate (E2), BZA, or TSEC (E2 plus BZA), to assess early and late B-cell development and to determine histological disease manifestations in the kidneys and salivary glands. Results TSEC treatment reduced the frequency of the pre-BI population in bone marrow to levels equivalent to treatment with physiological doses of E2 alone but did not affect any of the other examined B-cell populations. Our earlier studies indicated that TSEC treatment did not aggravate disease development in ovariectomized MRL/lpr mice, while protecting against trabecular bone loss. Here, we follow up on our previous study and show that neither ovariectomy alone nor TSEC treatment of ovariectomized MRL/lpr mice influenced perivascular lymphocyte infiltration to the kidneys or salivary glands. Conclusion TSEC does not aggravate a mouse model of lupus, when given in doses that protect against postmenopausal lupus-associated bone loss. This indicates that further investigations into TSEC as a treatment for osteoporosis or vasomotor symptoms in postmenopausal women with SLE are warranted.

Gastrointestinal digestion and absorption of soybean β-conglycinin in an early weaned piglet model: An initial step to the induction of soybean allergy.

To date, it still remains unknown how β-conglycinin, a major soybean allergen, crosses intestinal epithelial barrier to reach immune cells. The purpose of this study was to elucidate the pathway and molecular mechanism of β-conglycinin absorption and transport across intestinal mucosal epithelium using a β-conglycinin allergic piglet model. Ten-day old piglets were orally sensitized with diets containing 2% and 4% β-conglycinin. The digestion, absorption and transport of β-conglycinin in gastrointestinal tract was investigated. The results showed that β-conglycinin had a certain resistance to gastrointestinal digestion, and the digestion-resistant subunits and fragments were absorbed into the intestinal mucosa and then induced an anaphylaxis in early weaned piglets. The absorption occurred in the form of IgE-allergen immune complex through transcellular pathway with CD23 as the receptor. These results provided important clues for using the pathway and molecule as inhibitor target to prevent and alleviate soybean β-conglycinin allergy in infants.

PF4 activates the c-Mpl–Jak2 pathway in platelets

AbstractPlatelet factor 4 (PF4) is an abundant chemokine that is released from platelet α-granules on activation. PF4 is central to the pathophysiology of vaccine-induced immune thrombocytopenia and thrombosis (VITT) in which antibodies to PF4 form immune complexes with PF4, which activate platelets and neutrophils through Fc receptors. In this study, we show that PF4 binds and activates the thrombopoietin receptor, cellular myeloproliferative leukemia protein (c-Mpl), on platelets. This leads to the activation of Janus kinase 2 (JAK2) and phosphorylation of signal transducer and activator of transcription (STAT) 3 and STAT5, leading to platelet aggregation. Inhibition of the c-Mpl–JAK2 pathway inhibits platelet aggregation to PF4, VITT sera, and the combination of PF4 and IgG isolated from VITT patient plasma. The results support a model in which PF4-based immune complexes activate platelets through binding of the Fc domain to FcγRIIA and PF4 to c-Mpl.

Complement.

The role of complement in human autoimmune, inflammatory, and infectious diseases is reviewed, focusing on clinical applicability. A typical case is presented in which serum testing for C3 and C4 is performed to help assess a syndrome with a broad differential diagnosis. The review includes a discussion of complement deficiency states, consumption of complement by diseases characterized by immune-complex formation and deposition, usefulness and interpretation of laboratory tests for complement, and development of drugs targeting specific components of the complement pathway for a growing number of indications.

Apoptosis in post-streptococcal glomerulonephritis and mechanisms for failed of inflammation resolution.

Post-streptococcal glomerulonephritis is a condition resulting from infection by group A beta-hemolytic streptococcus. The main mechanism involves the formation of immune complexes formed in the circulation or in situ on the glomerular basement membrane, which activates complement and causes various inflammatory processes. Cellular mechanisms have been reported in the induction of kidney damage represented by the infiltration of innate cells (neutrophils and monocyte/macrophages) and adaptive cells (CD4 + lymphocytes and CD8 + lymphocytes) of the immune system. These cells induce kidney damage through various mechanisms. It has been reported that nephritogenic antigens are capable of inducing inflammatory processes early, even before the formation of immune complexes. Usually, this disease progresses towards clinical and renal normalization; however, in a smaller number of patients, it evolves into chronicity and persistent kidney damage. Hypotheses have been proposed regarding the mechanisms underlying this progression to chronicity including failure to induce apoptosis and failure to phagocytose apoptotic cells, allowing these cells to undergo membrane permeabilization and release pro-inflammatory molecules into the environment, thereby perpetuating renal inflammation. Other mechanisms involved include persistent infection, genetic background of the host's complement system, tubulointerstitial changes, and pre-existing kidney damage due to old age and comorbidities.

Von Willebrand factor modulates immune complexes and the recall response against factor VIII in a murine hemophilia A model

AbstractAchieving tolerance toward factor VIII (FVIII) remains an important goal of hemophilia treatment. Up to 40% of patients with severe hemophilia A (HA) develop neutralizing antibodies against FVIII, and the only proven treatment to achieve tolerance is infusion of FVIII over prolonged periods in the context of immune tolerance induction. Here, we addressed the role of von Willebrand factor (VWF) as a modulator of anti-FVIII antibody effector functions and the FVIII-specific recall response in an HA mouse model. Analytical ultracentrifugation was used to demonstrate formation of FVIII-containing immune complexes (FVIII-ICs). VWF did not fully prevent FVIII-IC formation but was rather incorporated into larger macromolecular complexes. VWF prevented binding of FVIII-ICs to complement C1q, most efficiently when it was preincubated with FVIII before the addition of antibodies. It also prevented binding to immobilized Fc-γ receptor and to bone marrow–derived dendritic cells. An in vitro model of the anti-FVIII recall response demonstrated that addition of VWF to FVIII abolished the proliferation of FVIII-specific antibody-secreting cells. After adoptive transfer of sensitized splenocytes into immunocompetent HA mice, the FVIII recall response was diminished by VWF. In summary, these data indicate that VWF modulates the formation and effector functions of FVIII-ICs and attenuates the secondary immune response to FVIII in HA mice.