Peripheral Blood B-cell Research Articles

B-cell and plasma cell activation in a mouse model of chronic muscle pain

Fibromyalgia (FM) is a complex chronic musculoskeletal pain disorder with an elusive pathogenesis, with a strong implication of immune interactions. We recently found that IL-5 and the adaptive immune system mediates pain outcomes in fibromyalgia (FM) patients and preclinical models of FM-like chronic widespread pain (CWP). However, there is an active debate if FM/CWP has an autoimmune etiology. Preclinical models of CWP utilize a repeated insult paradigm, which resembles a primary, then secondary response similarly observed in the antibody response in which the subsequent event causes a potentiated pain response. Recent translational studies have implicated immunoglobulins (Ig) and B-cells in FM/CWP pathophysiology. To understand if these are involved in preclinical models of CWP, we performed comprehensive B-cell phenotyping in the bone marrow, circulation, and popliteal (draining) lymph nodes in the two-hit acidic saline model of CWP. We found increased MHC class II-expressing B-cells in peripheral blood, increased activated plasma cells in peripheral blood, and increased memory B-cells in the bone marrow. Interestingly, acidic pH (4.0) injected mice have reduced levels of IgG1, independent of treatment with IL-5. We have demonstrated that the acidic saline model of CWP induces T-cell mediated activation of B-cells, increased active plasma cells, and increased memory B-cells in female mice.

Dexmedetomidine induces IL-10 secretion by B lymphocytes in the peripheral blood of patients with hepatocellular carcinoma

Background/aimTo investigate the distribution of subpopulations of peripheral blood B lymphocytes in individuals with hepatocellular carcinoma (HCC), and to evaluate the effect of dexmedetomidine (DEX) on B lymphocyte differentiation in patients with HCC in vitro. MethodsPeripheral blood mononuclear cells (PBMCs) were collected from the HCC group and the healthy group, and the distribution of peripheral blood B-lymphocyte subpopulations in the two groups was examined by Flow Cytometry (FCM). B lymphocytes extracted from the peripheral blood of the HCC group were divided into D0, D1, D2 and D4 groups according to the different dose of DEX in the culture medium (0 μM, 1 μM, 2 μM and 4 μM). After 72 h of in vitro culture, FCM was used to detect differences in the percentage of apoptotic B lymphocytes and the percentage of B lymphocytes that can express interleukin 10(IL-10) and transforming growth factor-β (TGF-β) in each group. ResultsIn contrast to the healthy group, the HCC group exhibited a statistically significant increase in the proportion of CD19 + CD73 + B lymphocyte subpopulation (P<0.05). In the in vitro culture experiment, the differences in apoptosis of B lymphocytes and the percentage of TGF-β expression in each group were not statistically significant; When compared to the control group, there was a significant increase in the percentage of B lymphocytes expressing IL-10 across the D1, D2, and D4 groups (P<0.05). ConclusionThe peripheral blood of HCC patients is characterized by an elevated presence of CD19 + CD73 + B lymphocyte subpopulations; DEX may have an immunosuppressive effect by promoting IL-10 secretion from peripheral blood B lymphocytes of HCC patients.

Multi-dimensional analysis of B cells reveals the expansion of memory and regulatory B cell clusters in humans living in rural tropical areas.

B-cells play a critical role in the formation of immune responses against pathogens by acting as antigen-presenting cells, by modulating immune responses and by generating immune memory and antibody responses. Here, we studied B-cell subset distributions between regions with higher and lower microbial exposure, i.e. by comparing peripheral blood B-cells from people living in Indonesia or Ghana to those from healthy Dutch residents using a 36-marker mass cytometry panel. By applying an unbiased multidimensional approach, we observed differences in the balance between the naïve and memory compartments, with higher CD11c+ and double negative (DN-IgDnegCD27neg) memory (M)B-cells in individuals from rural tropical areas, and conversely lower naïve B-cells compared to residents from an area with less pathogen exposure. Furthermore, characterization of total B-cell populations, CD11c+, DN and Breg cells showed the emergence of specific memory clusters in individuals living in rural tropical areas. Some of these differences were more pronounced in children compared to adults and suggest that a higher microbial exposure accelerates memory B cell formation, which 'normalizes' with age.

Association of CD24, CD27, and co-stimulatory molecules CD80 immunological marker expression on B-cells of human peripheral blood with development of celiac disease

Abstract: BACKGROUND: B-cells express a variety of clusters of differentiation markers during development. These markers determine the basic function of the immune phenotype specific to B-cells. Changes in the expression of these markers are linked to the development of many diseases, including chronic inflammation, autoimmune diseases, and immunodeficiency. OBJECTIVE: The current study aimed to investigate a change in CD24, CD27, and co-stimulatory molecules CD80 expression on peripheral blood B-cells and the extent of their contribution to celiac disease. MATERIALS AND METHODS: A total of 60 male children, whose ages ranged between 8 and 14 years, participated in this study. Thirty-five were identified as having celiac disease, while the control group comprised 25 children with anti-tissue transglutaminase (TG) (immunoglobulin G [IgG]), anti-tissue TG (IgA), and deamidated gliadin peptide (DGP) IgG levels normal. The frequency CD24, CD27, and CD80 expression were measured by flow cytometry. RESULTS: Celiac disease patients showed a substantial decrease in the percentage of CD24, CD27, and CD80 expression on B-cells compared to control groups. CONCLUSION: These findings suggest that numerical deficiency of CD24, CD27, and CD80 expression on B-cells in the peripheral blood mononuclear cell population, that may involve the loss of auto-tolerance that plays an important role in the immune response associated with inflammation and tissue damage in celiac disease. These immunological markers may be used as diagnostic indicators for this disease.

Features of T-cell and humoral immunity of patients with acute coronary syndrome, with and without COVID-19, depending on/peripheral blood B-lymphocytes with the phenotype CD3–CD19+CD5+ level

The aim of the work was to assess the T-cell and humoral immune arms in patients with acute coronary syndrome (ACS) recovered from or not exposed to COVID-19. 86 men with ACS aged 40 to 65 years old, who suffered or not exposed to COVID-19, which required stenting of coronary arteries, were examined. Depending on the peripheral blood B-lymphocyte CD3–CD19+CD5+ level and the former COVID-19 history, all patients were divided into 6 groups. Of the previously COVID-19 exposed subjects CD3–CD19+CD5+ lymphocytes were at: reduced (group 1), normal (group 2), increased (group 3) level. COVID-19 unexposed subjects had CD3–CD19+CD5+ lymphocyte level: reduced (group 4), normal (group 5), increased (group 6). The most severe clinical manifestations were observed in group 1: with a larger rate of stent thrombosis and increased mortality. In absolute numbers, T-lymphocytes were significantly lower in group 1 compared to other groups, except group 4. The lowest both relative and absolute T-helper cell counts were recorded in covid-19 patients, with reduced CD3–CD19+CD5+ cell level. NK-lymphocytes both in relative and absolute level were significantly (p 0.05) higher in patients who suffered from COVID-19 as compared to those in patients unexposed to previous COVID-19. Percentage of late-activation T-regulatory cells was minimal in patients with former COVID-19 along with high B-lymphocyte CD3–CD19+CD5+ level, which significantly (p 0.05) differed from those in subjects lacking former COVID-19 history. In addition, significantly lower B-lymphocyte CD3–CD19+CD5– level was found in group 1 and 4. The IgM level peaked in group 5 — subjects lacking former COVID-19 history and having normal CD3–CD19+CD5+ cell level that significantly differed in comparison with that of in group 1, 2, 3. At the same time, the maximum value of IgG level was recorded in COVID-19 patients with normal CD3–CD19+CD5+ cells, and significantly differed from those found in group 5 and 6. C1-inhibitor level was higher in group 3 that significantly differed from that in other groups. SARS-CoV-2-specific IgG and IgM levels were significantly higher in COVID-19-positive vs. COVID-19-negative patients. Conclusion. In patients who have suffered COVID-19 with low B-lymphocyte CD3–CD19+CD5+ level, a significantly compromised immune protection was noted in comparison with other groups: a decline in total T-lymphocyte, T-helper, early- and late-activation T-lymphocyte, T-regulatory cell, B-lymphocyte CD3–CD19+CD5– levels, which was associated with a more severe disease course characterized by stent thrombosis and large mortality.

Biomarkers for Radiation Biodosimetry and Correlation with Hematopoietic Injury in a Humanized Mouse Model.

After a large-scale radiological or nuclear event, hundreds of thousands of people may be exposed to ionizing radiation and require subsequent medical management. Acute exposure to moderate doses (2-6 Gy) of radiation can lead to the hematopoietic acute radiation syndrome, in which the bone marrow (BM) is severely compromised, and severe hemorrhage and infection are common. Previously, we have developed a panel of intracellular protein markers (FDXR, ACTN1, DDB2, BAX, p53 and TSPYL2), designed to reconstruct absorbed radiation dose from human peripheral blood (PB) leukocyte samples in humanized mice up to 3 days after exposure. The objective of this work was to continue to use the humanized mouse model to evaluate biomarker dose-/time- kinetics in human PB leukocytes invivo, at an earlier (day 2) and later (day 7) time point, after exposure to total-body irradiation (TBI) doses of 0 to 2 Gy of X rays. In addition, to assess hematological sensitivity and radiation-induced injury, PB leukocyte cell counts, human BM hematopoietic stem cell (HSC) and progenitor cell [multipotent progenitor (MPP), common myeloid progenitor (CMP), granulocyte myeloid progenitor (GMP), megakaryocyte/erythrocyte progenitor (MEP) and multi-lymphoid progenitor (MLP)] levels were measured, and their correlation was also examined as the BM damages are difficult to assess by routine tests. Peripheral blood B-cells were significantly lower after TBI doses of 0.5 Gy on day 2 and 2 Gy on days 2 and 7; T-cells were significantly reduced only on day 2 after 2 Gy TBI. Bone marrow HSCs and MPP cells showed a dose-dependent depletion after irradiation with 0.5 Gy and 2 Gy on day 2, and after 1 Gy and 2 Gy on day 7. Circulating B cells correlated with HSCs, MPP and MLP cells on day 2, whereas T cells correlated with MPP, and myeloid cells correlated with MLP cells. On day 7, B cells correlated with MPP, CMP, GMP and MEP, while myeloid cells correlated with CMP, GMP and MEP. The intracellular leukocyte biomarkers were able to discriminate unirradiated and irradiated samples at different time points calculated by receiver operating characteristic (ROC) curve. Using machine learning algorithm methods, combining ACTN1, p53, TSPYL2 and PB-T cell and PB-B cell counts served as a strong predictor (area under the ROC >0.8) to distinguish unirradiated and irradiated samples independent of the days after TBI. The results further validated our biomarker-based triage assay and additionally evaluated the radiation sensitivity of the hematopoietic system after TBI exposures.

FCGR3A-V158F gene polymorphism: A potential predictor for rituximab dosing optimization in Chinese patients with neuromyelitis optica spectrum disorder

BackgroundRituximab (RTX), an anti-CD20 monoclonal antibody, has shown promise in managing neuromyelitis optica spectrum disorders (NMOSD) by depleting B cells and reducing relapses. However, there is no consensus on the optimal RTX dosing regimen, and genetic factors, such as FCGR3A-V158F polymorphism, may influence treatment outcomes. This study investigates how FCGR3A-V158F genotypes influence RTX efficacy in Chinese NMOSD patients under varying dosing regimens and aims to optimize treatment protocols. MethodsWe conducted a retrospective analysis of 25 Chinese NMOSD patients treated with RTX, grouped into standardized and low-dosage regimens. FCGR3A-V158F genotypes were determined, and treatment responses were evaluated, including relapse rates, time to first relapse (TFR), B-cell depletion, dose adjustments, and treatment retention. ResultsAmong all patients, 15 received standardized dosages, while 10 received varied induction doses (500 mg to 1200 mg) in low-dose regimens. For FCGR3A-V158F genotypes, 15 had the FF genotype, and 10 were V carriers (3 VV genotype, 7 VF genotype). Regardless of dosing, FF genotype patients had a higher relapse rate post-RTX treatment compared to V carriers (P < 0.05). None of the 3 VV genotype patients in either dose group experienced relapses post-RTX. In both dose groups, FF genotype patients had significantly shorter TFR and required more RTX dose adjustments post-RTX treatment compared to V carriers in the standardized dosage group (P < 0.05). FF genotype patients in the low dosage group were more likely to experience insufficient B-cell depletion, had lower treatment retention rates, and more discontinuations than V carriers in the standardized dosage group (P < 0.05). Insufficient B-cell depletion significantly predicted clinical relapses after RTX treatment (P < 0.05). In survival analysis, FF genotype patients, regardless of dosing, experienced earlier relapses post-RTX treatment (P < 0.05). ConclusionsThis study highlights the importance of RTX dosage selection in NMOSD treatment, particularly for FCGR3A-FF genotype patients. Standard-dose RTX therapy with vigilant monitoring of peripheral blood B-cell levels is recommended for these individuals to optimize treatment efficacy.

Abstract 6409: A multiparametric flow cytometry assay to monitor regeneration of B-cells following anti B-cell therapy in cancer and autoimmune patients

Abstract Purpose Functional dysregulation of B-cells leads to a variety of autoimmune disorders and blood cancers. Multiple B-cell depleting therapies (e.g., BTK inhibitors, antibodies or CAR-Ts) are currently in active clinical trial investigation. Following therapeutic elimination of pathogenic B-cells, it is critical to monitor the productive regeneration of fully functional B-cells as they mediate innate and adaptive immune responses. To this end, we developed a multiparametric flow cytometry assay for exquisite monitoring of early stages of B cell development, maturation, and antibody production to correlate it with treatment outcomes and determine if continuous depletion of B-cells is necessary to maintain clinical benefits for patients. Study Design We designed a high throughput 12-parameter flow cytometry panel incorporating primary differentiation markers namely, CD45, CD3, CD38, CD10, CD27, CD19, CD20, IgD, Lambda &amp; Kappa Light Chains required for identification of different developmental stages of B-cells in peripheral blood using an in vitro diagnostic grade flow cytometry system (BD FACSLyric). The optimized method underwent robust fit-for-purpose analytical validation per CLSI H62 guidelines with emphasis on establishing assay sensitivity, specificity, and reproducibility across experimental days, operators, and instruments. Results We were able to reliably identify different stages of B-cell development, namely, Naïve (CD19+CD20+IgD+CD27-), Unswitched/Marginal (CD19+CD20+IgD+CD27+), Memory (CD19+CD20+IgD-CD27+), Transitional (CD19+CD20+IgD+CD27-CD10+), Antibody Secreting Cells (CD19+CD20-IgD-CD27+CD38hi) as well as clonality (CD19+CD20+Lambda+ or Kappa+). The lower limit of quantitation was determined to be around 60 events, based upon analysis of 90 data points with good reproducibility (CV range: 0-11.7%) across experimental days, operators and instruments demonstrating sensitive detection and robust performance. Conclusion In summary, we have developed and validated a 12-parameter flow cytometry assay focusing on monitoring the regeneration of different subsets of B-cells in various B-cell malignancies (Non-Hodgkin’s Lymphoma, B CLL) and autoimmune disorders (Multiple Sclerosis, Rheumatoid Arthritis, Systemic Lupus Erythematosus). The high reproducibility/robustness of the assay demonstrates its suitability for use in clinical trials as a valuable tool for safety monitoring and disease evaluation enabling development of novel therapeutic agents. Citation Format: Amit Kumar Mehta, Ruby Tandon, Anil Pahuja, Jane Gao, Kevin Nguyen, Naveen Dakappagari, Zeni Alfonso. A multiparametric flow cytometry assay to monitor regeneration of B-cells following anti B-cell therapy in cancer and autoimmune patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6409.

Peripheral Blood B-Cell Subsets Frequency and Distribution and the BSF-2(IL-6) to CSIF:TGIF(IL-10) Ratio as Severity-Associated Signatures in Primary Open-Angle Glaucoma: A Case-Controlled Study.

Flow cytometry was used to determine B-cell subset frequencies from 30 POAG patients grouped by hierarchical cluster analysis or the mean deviation (MD) of the visual field (VF) and correlated with the patients' clinical and pathological data, as well as with BSF-2(IL-6) and CSIF:TGIF(IL-10), which were quantified in peripheral blood samples of patients and controls by ELISA. The total B-cell frequency was increased in the POAG group in comparison to the control group (n = 30). Frequencies of specific B-cell subsets, such as double-negative (DN) and naïve B-cell subsets, were increased in relation to the severity of the POAG disease. However, the unswitched memory B compartment subset decreased in the POAG group. Other non-typical B-cell subsets such as DN B cells also showed significant changes according to the POAG disease severity course. These differences allow us to identify POAG severity-associated inflammatory clusters in patients with specifically altered B-cell subsets. Finally, ocular parameters, biomarkers of inflammation, and other glaucoma-related or non-clinical scores exhibited correlations with some of these B-cell subpopulations. The severity of the POAG disease course is accompanied by changes in the B-cell subpopulation, namely, DN B cells. Furthermore, the existing relationship of the B-cell subset frequencies with the clinical and the inflammatory parameters BSF-2(IL-6), CSIF:TGIF(IL-10), and the BSF-2(IL-6) to CSIF:TGIF(IL-10) ratio suggests that these B lymphocyte cells could serve as potential molecular bio-markers for assessing POAG disease severity and/or progression.

Tobacco exposure, but not aging, shifts the frequency of peripheral blood B cell subpopulations.

Several disturbances in T-cell mediated immunity have been described during aging, but immunosenescence of the B-cell compartment is less well elucidated. The peripheral blood B-cell compartment (CD19+) can be split into six main subpopulations according to the cell surface markers IgD, CD27, CD24, and CD38: Transitional, naïve, unswitched, switched, double negative and plasmablasts. We thus aimed to verify whether shifts in these subsets occur during healthy and pathological aging. We recruited three groups of aged people (> 60 years old), healthy, COPD patients, and smokers without altered pulmonary function test, and a fourth group of individuals 18-40 years old (youngs). Total B-cells percentage and absolute number were similar among the healthy aged, COPD patients, and youngs, but the smokers showed significantly higher absolute numbers. While all six B-cell subset percentages were comparable among the healthy aged, COPD patients, and youngs, smokers showed significantly higher percentages of switched B-cells and reduced naïve B-cells than the other three groups, resulting in an inverted naive:switched ratio. Analysis of the cell subset absolute numbers showed a similar trend. Overall, our results suggest that aging drives milder alterations in the distribution of peripheral blood B-cell subpopulations than in the T-cell compartment. We suggest that it is the T-cell immunosenescence that most contributes to the poor humoral immune responses in the elderly, vaccine responses included. Surprisingly it was the smokers who showed significant alterations when compared with the youngs, healthy aged, and aged COPD patients, probably as a result of the chronic immune stimulation described in active smoking subjects.

Comparison of the CXCR5-Antibody Drug Conjugate (ADC; VIP924) to a CD19-ADC and a CD79b-ADC in a Humanized Rec-1 Mantle Cell Lymphoma (MCL) Mouse Model

Introduction The chemokine receptor CXCR5 is highly expressed in MCL, which is a rare subtype of non-Hodgkin lymphoma. VIP924 is a first-in-class CXCR5-targeting ADC composed of a legumain-cleavable linker and a kinesin spindle protein inhibitor (KSPi) payload. We compared VIP924 with a CD19- and a CD79b- targeting ADC in a humanized mouse model of MCL. Methods Expression of CXCR5 and the B-cell targets CD19 and CD79b were analyzed on tumor samples from patients with MCL using immunohistochemistry. Slides were examined by a pathologist and scored for expression. NSG-SGM3 mice were transplanted with human hematopoietic stem cells from 4 different donors and after engraftment transplanted subcutaneously with REC-1 MCL cells into their flanks. When subcutaneous tumors reached a size of 100 mm 3, mice were randomized into 5 groups and treated with 10 mg/kg of an isotype control ADC, 3 mg/kg polatuzumab vedotin, 0.66 mg/kg loncastuximab teserine, 3 mg/kg VIP924, or 10 mg/kg VIP924 every 5 days for 4 doses. Immunophenotyping of peripheral blood was performed by flow cytometry before starting treatment (Day 0) and on Day 5 and Day 18 during the treatment. At the end of the experiment, immunophenotyping was also done on tumors, spleen, and bone marrow. Complete blood count was analyzed based on single cell evaluation (Drew Scientific HemaVet 950FS Auto Blood Analyzer). Results By immunohistochemistry CXCR5 and CD19 showed comparable high expression on patient samples, whereas CD79b expression was moderate. Treatment of humanized mice bearing REC-1 tumors with VIP924 at 10 mg/kg reduced tumor growth effectively (p&amp;lt;0.0001 vs. isotype control on Day 10), while treatment with polatuzumab vedotin and loncastuximab teserine showed no effects on tumor growth. This outcome was also reflected in the median survival rates for the different groups with 17 days for isotype control and polatuzumab vedotin, 14 days for loncastuximab teserine and not reached for the 10-mg/kg VIP924 group. However, polatuzumab vedotin treatment significantly reduced hCD45+ cells in peripheral blood and spleen, while loncastuximab teserine treatment showed a clear trend for reduction. VIP924 treatment in both arms had no effect on peripheral or splenic hCD45+ cells. All tested ADCs reduced the CD19+ and more mature CD19+/CXCR5+ B-cells in peripheral blood and spleen, with polatuzumab vedotin and loncastuximab teserine showing significant (p&amp;lt;0.0001 vs. isotype control on Day 18) effects on CD19+ cell reductions, while VIP924 treatment showed a milder reduction in CD19+ cells (p= 0.0051 for 3 mg/kg and p= 0.0407 for 10 mg/kg VIP924). Loncastuximab teserine treatment increased the amount of myeloid derived suppressor cells in the peripheral blood significantly (p= 0.0467). In contrast, VIP924 led to a significant (p&amp;lt; 0.0001) increase in peripheral regulatory T-cells compared with isotype control. Complete blood counts from treated mice showed a reduction of white blood cells (WBC), absolute lymphocyte count, and absolute monocyte count in loncastuximab teserine-treated animals. Loncastuximab teserine treatment also reduced red blood cell count and hemoglobin values. In VIP924-treated animals, no effects on WBC, red blood cell count, or hemoglobin values were observed. All treatments showed no detrimental effects on body weights of the mice. Conclusion CXCR5 is a highly attractive target in B-cell malignancies such as diffuse large B-cell lymphoma and MCL due to high CXCR5 surface expression. VIP924, a CXCR5-targeting ADC, showed high potency and superiority to other B-cell-targeted ADCs in a humanized mouse model of MCL. In this MCL model in humanized mice, VIP924 at 10 mg/kg treatment showed a significant reduction in tumor growth and improvement in survival, while polatuzumab vedotin and loncastuximab teserine had no effect on tumor growth or survival. Interestingly, VIP924 was the only ADC to cause a significant increase in peripheral T regulatory cells, which may enhance tumor growth inhibition. Loncastuximab teserine had a deleterious effect on several hematologic parameters, which was not observed with VIP924 or polatuzumab vedotin. The efficacy and tolerability observed in this study with VIP924 suggests further testing in human clinical trials is warranted.

TLR1-10 Protein Expression in Circulating Human White Blood Cells during Bacterial and COVID-19 Infections

Toll-like Receptors (TLR) are major sensors of the innate immune system and are involved in the recognition of Pathogen Associated Molecular Patterns (PAMPs) and Damage Associated Molecular Patterns (DAMPs). When activated, TLR signaling pathways trigger an intracellular response that leads to the production of pro-inflammatory cytokines, chemotactic factors, antimicrobial peptides, and interferons. Overexpression of certain TLRs on neutrophils has been associated with increased mortality in patients with infection-induced shock, although the role of TLR4 overexpression is still debated. While TLRs play a role in recognizing in bacterial structures, they can also detect viral patterns, particularly TLR2, TLR3, and TLR7. The activation of the TLR signaling pathway is an early step recognizing viral genomic patterns of SARS-CoV-2 and its spike protein activates TLR4. In this prospective single-center observational cohort study, we conducted a comprehensive analysis of the protein expression of the ten known human TLR in white blood cells from patients with either bacterial and viral infections using flow cytometry, together with CD180, a 95-105 kDa TLR-like glycoprotein expressed on peripheral blood monocytes and B-lymphocytes. 73 patients were included, divided into 4 groups based on infection severity (sepsis, septic shock, moderate and severe COVID-19), along with 7 control subjects. Septic shock was assessed according to the third international consensus definition. COVID-19 patients with confirmed SARS-CoV-2 infection using reverse transcriptase-polymerase chain reaction (RT-PCR), admitted either to the emergency department (ED) or in the ICU were included. This study protocol was reviewed and approved by the local ethic committee, and written informed consent was obtained from participants of their relatives. For endosomal TLRs (TLR3, TLR7, TLR8, TLR9), plasma cell permeabilization was performed using the Perm2 Solution® (BD Biosciences, USA) prior to incubation of monoclonal antibodies staining. Cell surface expression was studied for the other TLRs. In neutrophils, antibody staining for TLR1-10 and CD180 revealed the expression of TLR4, with a large variation in positivity between groups, TLR8, TLR9 were also expressed, while TLR2, TLR3, and TLR7 were weakly expressed. In monocytes, only TLR2, TLR4, and CD180 were detected Notably, we observed a significant reduction in the expression of TLR4 and its co-receptor CD14 in neutrophils of patients with shock compared to controls (MFI=19 273 vs. 111 691, p&amp;lt;0.001 and MFI 2 028 vs. 3 025, p &amp;lt;0.02 respectively). Furthermore, severe COVID-19 patients exhibited a significant increase in TLR3 and TLR7 levels in neutrophils (p=0.003 and p=0.02 respectively) compared to the control group. Patients with shock also showed a similar increase in TLR7 expression in neutrophils, along with elevated intermediate monocytes compared to controls. TLR expression remained unchanged in lymphocytes. We also observed that CD16 expression in neutrophils was significantly lower in septic shock patients compared to healthy donors (p&amp;lt;0.0001), and to a lesser extent in sepsis patients (p&amp;lt;0.01), consistent with previous studies This study provided further insights into the mechanisms of TLR activation in various severe forms of infection. Additional analysis is required to assess their correlation with patient outcomes and evaluate the potential impact of TLR-related therapy on neutrophils activation.

Characterization of Three Somatic Mutations in the 3'UTR of RRAS2 and Their Inverse Correlation with Lymphocytosis in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is a hematologic malignancy characterized by progressive accumulation of a rare population of CD5+ B-lymphocytes in peripheral blood, bone marrow, and lymphoid tissues. CLL exhibits remarkable clinical heterogeneity, with some patients presenting with indolent disease and others progressing rapidly to aggressive CLL. The significant heterogeneity of CLL underscores the importance of identifying novel prognostic markers. Recently, the RAS-related gene RRAS2 has emerged as both a driver oncogene and a potential marker for CLL progression, with higher RRAS2 expression associated with poorer disease prognosis. Although missense somatic mutations in the coding sequence of RRAS2 have not been described in CLL, this study reports the frequent detection of three somatic mutations in the 3' untranslated region (3'UTR) affecting positions +26, +53, and +180 downstream of the stop codon in the mRNA. An inverse relationship was observed between these three somatic mutations and RRAS2 mRNA expression, which correlated with lower blood lymphocytosis. These findings highlight the importance of RRAS2 overexpression in CLL development and prognosis and point to somatic mutations in its 3'UTR as novel mechanistic clues. Our results may contribute to the development of targeted therapeutic strategies and improved risk stratification for CLL patients.

Poor Hematopoietic Reserve at the Time of CD19 CAR T-Cell Infusion Is Associated with Long Term B-Cell Aplasia

Background: On-target off-tumor toxicities of anti-CD19 CAR T-cell therapy include B-cell aplasia and hypogammaglobulinemia. Long term B-cell aplasia is hypothesized to represent functional CAR T-cell engraftment (Melenhorst, Nature 2022), while peripheral blood B-cell recovery represents the loss of functional CAR-T cells against target over time. Patients with large B-cell lymphoma (LBCL) who are clinical responders have a 50-70% chance of B-cell recovery in the first year, with the remainder experiencing longer term B-cell aplasia (Logue, Haematologica 2021). Here, we sought to identify factors associated with long term B-cell aplasia using a cohort of responding patients who received CAR T-cell therapy for LBCL. Methods:This retrospective cohort study included 57 patients with LBCL treated with CD19-targeted CAR T-cell therapy between June 2016 and August 2020 at Moffitt Cancer Center who exhibited complete or partial response at six months after CAR T-cell infusion. Patients were treated with with axicabtagene ciloleucel (axi-cel; n=50) or tisagenlecleucel (tisa-cel; n=7), either as standard-of-care therapy (n=47) or as part of a previously published clinical trial (n=10; NCT02348216, NCT03391466, NCT03153462). Peripheral blood B-cells were measured by flow cytometry using CD19 expression as part of routine clinical care at baseline and periodically after infusion. Prolonged B-cell aplasia was defined as a CD19+ B cell count comprising less than 1% of peripheral blood mononuclear cells during a minimum of two separate time points beyond 6 months of follow-up. Patients were defined as having B cell recovery if &amp;gt;1% B-cells were observed in peripheral blood at any time after CAR T-cell infusion. Results: At a median follow up of 33 months (95% CI: 28.7, 37.3 months), 29 (51%) patients had persistent B-cell aplasia and 28 (49%) had recovery of peripheral B-cell counts. Median B-cell count at 12 months in the recovery group was 84/µL (IQR 2.5-197) compared to 0/µL (IQR 0-1) in the aplasia group. Patients with long-term B-cell aplasia had lower CD4 T-cell counts prior to CAR T-cell infusion [median 200/µL (IQR 136-278) vs. 330/µL (IQR 224-451); P= 0.008] and over time compared to patients with B-cell recovery (Fig. A). Patients with long-term B cell aplasia also had lower pre-infusion absolute neutrophil counts (2.3K/µL (IQR 1.4-4.15) vs. 3.5K/µL (IQR 2.8-4.2); P&amp;lt;0.001) and higher baseline CAR-HEMATOTOX scores [2 (IQR 1-3.25) vs 1 (IQR 0-1)], consistent with poor baseline hematopoietic reserve (Rejeski, Blood 2021). While disease-related mortality did not significantly differ between groups, non-relapse mortality was markedly higher in patients with long-term B-cell aplasia due to infection: all 8 patient deaths in the aplasia group were due to infections occurring beyond day 30 post-infusion, with 6 of the 8 deaths due to COVID-19. However, no patients in the B-cell recovery group died of late infection (Fig. B). Conclusions: Long term B-cell aplasia is hypothesized to represent ongoing CAR T-cell activity against normal B-cells. However, our results demonstrate that B-cell aplasia is associated with low baseline hematopoietic reserve and subsequent poor immune reconstitution of multiple lineages including B-cells, T-cells, and myeloid cells. Further studies are warranted to assess whether poor immune reconstitution and B-cell aplasia are related to long term CAR T-cell activity or other processes. These patients are at higher risk for non-relapse mortality from infection, and mitigation strategies are needed.

Mosunetuzumab Monotherapy Continues to Demonstrate Durable Responses in Patients with Relapsed and/or Refractory Follicular Lymphoma after ≥2 Prior Therapies: 3-Year Follow-up from a Pivotal Phase II Study

Background: Mosunetuzumab is a CD20xCD3 T-cell engaging bispecific antibody that redirects T cells to eliminate malignant B cells. In a pivotal Phase II study (NCT02500407), mosunetuzumab demonstrated a high complete response (CR) rate with a manageable safety profile in patients with relapsed/refractory (R/R) follicular lymphoma (FL) and ≥2 prior lines of therapy (Budde et al. Lancet Oncol 2022). Mosunetuzumab is a fixed-duration treatment that can be administered in an outpatient setting. Here, we present updated data for patients with R/R FL and ≥2 prior lines of therapy, after 3 years of follow-up. Methods: Eligible patients with R/R FL Grade (Gr) 1-3a and ≥2 prior therapies received intravenous mosunetuzumab in 21-day cycles with step-up dosing in Cycle (C) 1 (C1 Day [D] 1, 1mg; C1D8, 2mg; C1D15/C2D1, 60mg; C3D1 and onwards, 30mg). Hospitalization for treatment was not required. Patients achieving a CR by C8 completed treatment without additional cycles; patients with a partial response or stable disease received a total of 17 cycles. The primary endpoint was CR rate as determined by an Independent Review Committee (as best response; Cheson 2007 criteria). Duration of response (DOR), duration of complete response (DOCR), progression-free survival (PFS), event-free survival (EFS), and safety were secondary endpoints. Time to next treatment (TTNT), response to retreatment, biomarkers of minimal residual disease (MRD), and circulating B-cell counts were exploratory endpoints. Results: Ninety patients with R/R FL were enrolled. As of May 2, 2023, median time on study was 37.4 (range: 2.0-48.0) months. Investigator-assessed best overall response and CR rates were 77.8% (95% CI: 67.8-85.9) and 60.0% (95% CI: 49.1-70.2), respectively. The median DOR was 35.9 months (95% CI: 20.7-not reached [NR]). Median DOCR was NR (95% CI: 33.0-NR); the estimated 30-month DOCR rate was 72.4% (95% CI: 59.2-85.6) ( Table). Three years after the end of treatment, 57.1% of 70 responding patients were alive and disease progression-free. Median PFS was 24.0 months (95% CI: 12.0-NR) ( Figure). The median TTNT was 37.3 months (95% CI: 18.0-NR); estimated EFS at 36 months was 51.8% (95% CI: 40.8-62.8). After initial mosunetuzumab treatment, 34/90 (37.8%) patients had received a new anti-lymphoma therapy, including 33/90 (36.7%) patients who received a new systemic treatment (8/33 [24.2%] of these patients received chimeric antigen receptor T-cell therapy); 8/90 (8.9%) had radiotherapy; 2/90 (2.2%) had excision of tumor; 2/90 (2.2%) had an allogeneic stem cell transplant; and 1/90 (1.1%) had an autologous stem cell transplant. Five patients received retreatment with mosunetuzumab, 3/5 of these patients had a CR. No new cytokine release syndrome (CRS) events, serious, or Gr ≥3 adverse events (AEs) were reported since the previous analysis (median follow-up of 28.3 months; Bartlett et al. ASH 2022). CRS events occurred in 44.4% of patients and 2.2% were Gr 3/4 in severity; all CRS events resolved. Overall AEs and serious AEs were comparable to the previous analysis (Bartlett et al. ASH 2022); febrile neutropenia was not reported. Forty-six (51.1%) patients experienced Gr 3/4 AEs related to mosunetuzumab; the rate of AEs leading to discontinuation was low (4.4%). Peripheral blood B-cell depletion following treatment with mosunetuzumab occurred in all patients, and recovery was observed after a median of 18 months following the end of treatment in patients with a sustained response using follow-up samples. MRD kinetics following mosunetuzumab therapy will be presented. Conclusions: In this updated analysis, with a median follow-up of 37.4 months, durable responses continued to be observed with fixed-duration mosunetuzumab in patients with R/R FL. The manageable safety profile was consistent with previous reports. Evidence of B-cell recovery was observed after a median of 18 months following the end of treatment.

Abnormal immune function of B lymphocyte in peripheral blood of Parkinson's disease

BackgroundParkinson's disease (PD) is associated with peripheral inflammation and abnormal peripheral blood lymphocyte immune responses. Peripheral blood B-lymphocyte subset distributions and whether they are associated with PD are unclear. MethodsSixty-one PD patients and sixty-one one-to-one paired healthy controls (HCs) were enrolled. We used flow cytometry to perform immunophenotyping of peripheral B-lymphocyte, in vitro stimulation and measured serum cytokine. The relationship between variables and PD were assessed. ResultsThe percentage of naive B cells in blood of PD patients was decreased, whereas the percentages of regulatory B cells (Bregs), plasma blast cells (PBCs), and double-negative (DN) B cells were increased. The absolute counts of B-lymphocyte and naive B cells in blood of PD patients were decreased. Regression analysis revealed that alterations in the absolute counts of B-lymphocyte and the percentage of Bregs and DN B cells were associated with PD. After stimulation, the percentages of Bregs, PBCs, and switched memory (SwM) B cells increased in PD patients. Additionally, increases in GM-CSF-producing B-cell, IFN-γ-producing B-cell, and TNF-α-producing B-cell percentages were noted in PD. Serum levels of a proliferation-inducing ligand (APRIL), B-cell activating factor (BAFF) and soluble CD40 ligand (sCD40L) were elevated in PD and correlated negatively with the UPDRS III score. ConclusionsAbnormal B-lymphocyte immune responses in peripheral blood may contribute to PD development. Alterations in the absolute counts of B-lymphocyte and the percentage of Bregs and DN B cells are associated with PD. Furthermore, APRIL, BAFF, and sCD40L could be potential targets for intervention in PD.

Characterization of B-cell receptor clonality and immunoglobulin gene usage at multiple time points during active SARS-CoV-2 infection.

Although monoclonal antibodies to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are known, B-cell receptor repertoire and its change in patients during coronavirus disease-2019 (COVID-19) progression is underreported. We aimed to study this molecularly. We used immunoglobulin heavy chain (IGH) variable region (IGHV) spectratyping and next-generation sequencing of peripheral blood B-cell genomic DNA collected at multiple time points during disease evolution to study B-cell response to SARS-CoV-2 infection in 14 individuals with acute COVID-19. We found a broad distribution of responding B-cell clones. The IGH gene usage was not significantly skewed but frequencies of individual IGH genes changed repeatedly. We found predominant usage of unmutated and low mutation-loaded IGHV rearrangements characterizing naïve and extrafollicular B cells among the majority of expanded peripheral B-cell clonal lineages at most tested time points in most patients. IGH rearrangement usage showed no apparent relation to anti-SARS-CoV-2 antibody titers. Some patients demonstrated mono/oligoclonal populations carrying highly mutated IGHV rearrangements indicating antigen experience at some of the time points tested, including even before anti-SARS-CoV-2 antibodies were detected. We present evidence demonstrating that the B-cell response to SARS-CoV-2 is individual and includes different lineages of B cells at various time points during COVID-19 progression.

The Use of CD200 in the Differential Diagnosis of B-Cell Lymphoproliferative Disorders.

Background: B-Cell Lymphoproliferative Disorders (B-LPDs) are a group of heterogenous disorders characterised by the accumulation of B-cells in peripheral blood, bone marrow, lymph nodes and spleen. They have a variable disease course and outcome and many share similar features making differential diagnosis challenging. Therefore, accurate diagnosis is fundamental in particular for determining treatment options. Immunophenotyping by flow cytometry plays a crucial role in the diagnosis of B-LPDs. However, overlapping immunophenotyping patterns exist and the use of novel monoclonal antibodies has become increasingly important in immunophenotyping analysis. More recently differential expression of CD200 has been reported in various B-LPDs and that CD200 may improve the differentiation between chronic lymphocytic leukaemia (CLL) and mantle cell lymphoma (MCL). In this study CD200 expression is evaluated in different B-LPDs. Methods: A total of 100 samples were collected and analysed by immunophenotyping flow cytometry over a period of 1year (2017-2018), by a panel of monoclonal antibodies including CD200. The percentage of CD200 and its expression intensity was evaluated and compared between different groups of B-LPDs. Results: All of the 50 cases of CLL expressed CD200 with moderate to bright intensity, 6 MCL cases lacked the expression of CD200. Furthermore, all 5 cases of hairy cell leukaemia (HCL) expressed CD200. Out of all B-LPDs evaluated, CD200 expression in HCL cases was noted to be the brightest. The other 39 cases were not found to be B-LPDs. Conclusion: CD200 has an important role in differentiating CLL from MCL, HCL has a consistent bright expression of CD200. By adding CD200 to the combinations of markers in routine testing panel, Immunophenotyping by flow cytometry can be an effective tool in the diagnosis of B-LPDs especially in cases with atypical immunophenotyping pattern. Our result support that CD200 can be added to routine testing panel as it is useful in differentiating them.

Cytokine producing B-cells and their capability to polarize macrophages in giant cell arteritis

ObjectiveThe lack of disease-specific autoantibodies in giant cell arteritis (GCA) suggests an alternative role for B-cells readily detected in the inflamed arteries. Here we study the cytokine profile of tissue infiltrated and peripheral blood B-cells of patients with GCA. Moreover, we investigate the macrophage skewing capability of B-cell-derived cytokines. MethodsThe presence of various cytokines in B-cell areas in temporal artery (n = 11) and aorta (n = 10) was identified by immunohistochemistry. PBMCs of patients with GCA (n = 11) and polymyalgia rheumatica (n = 10), and 14 age- and sex-matched healthy controls (HC) were stimulated, followed by flow cytometry for cytokine expression in B-cells. The skewing potential of B-cell-derived cytokines (n = 6 for GCA and HC) on macrophages was studied in vitro. ResultsThe presence of IL-6, GM-CSF, TNFα, IFNγ, LTβ and IL-10 was documented in B-cells and B-cell rich areas of GCA arteries. In vitro, B-cell-derived cytokines (from both GCA and HC) skewed macrophages towards a pro-inflammatory phenotype with enhanced expression of IL-6, IL-1β, TNFα, IL-23, YKL-40 and MMP-9. In vitro stimulated peripheral blood B-cells from treatment-naïve GCA patients showed an enhanced frequency of IL-6+ and TNFα+IL-6+ B-cells compared to HCs. This difference was no longer detected in treatment-induced remission. Erythrocyte sedimentation rate positively correlated with IL-6+TNFα+ B-cells. ConclusionB-cells are capable of producing cytokines and steering macrophages towards a pro-inflammatory phenotype. Although the capacity of B-cells in skewing macrophages is not GCA specific, these data support a cytokine-mediated role for B-cells in GCA and provide grounds for B-cell targeted therapy in GCA.

#5639 TARGETING BAFF AND APRIL IN IGA-NEPHROPATHY

Abstract Background and Aims B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are critical factors in the differentiation and longevity maintenance of the B-cells pool thereby mediating humoral immunity. BAFF and APRIL are involved in initiating B-cells to become self-reactive and elevated levels of these cytokines are detected in the sera of patients with systemic autoimmune diseases. The aim of the study was to estimate role of APRIL and BAFF in IgA-nephropathy (IgAN) patients and to determine the appropriate IgAN treatment based on the assessment of BAFF and APRIL dynamics in IgAN patients’ sera after 6 months of different treatments. Method The 52 IgAN patients aged 32,0 (27,0; 36,0) y.o., male/female ratio as 34/18 despite using of renin-angiotensin-aldosterone system inhibitors (RAASIs) for 6 months with PU 1,8 (1,0; 1,9) g/day and estimated glomerular filtration rate (eGFR) 78 (61; 103) ml/min were divided into 3 treatment groups: 1 group (n = 20) – 200 mg hydroxychloroquine (HCQ) twice a day, 2 group (n = 20) – received glucocorticoids (GC) regimen Pozzi protocol, 3 group (n = 12) – received (RAASIs) in maximal tolerated dose. The control group included age- and sex-matched healthy donors (n = 10). The number of B-cells in peripheral blood was identified by flow cytometry method. The concentrations of total IgM, IgG, IgA, IgE, APRIL and BAFF were determined by ELISA method using commercial kits. Statistical analysis was done using Statistica 10.0. Results Despite the absence of statistically significant differences in the number of B-lymphocytes the increased levels of total IgM, IgA and IgE (p = 0,001) as well as APRIL (5336 (3574; 5965) pg/ml vs 4543 (4518 ÷ 4755) pg/ml (p = 0,05) and BAFF 378 (191; 541) vs 336 (257; 424) pg/ml (p = 0,07) were established in sera of IgAN patients as compared to control group, respectively. The initial APRIL level was correlated with the degree of tubular atrophy with interstitial fibrosis (R = 0,40, p = 0,05) and serum IgG level (R = 0,35, p = 0,05) in IgAN patients. After 6 months of treatment proteinuria was significantly reduced in HCQ (p = 0,03) and GC (p = 0,02) groups while kidney function was stable in all patients. The dynamic of immunological parameters is presented in the Table 1. It was established that HCQ treatment in IgAN patients decreased the production of IgM (p = 0,01) and IgG (p = 0,02) as well as serum concentration of the APRIL factor (p = 0,05) what correlated with the tendency to eGFR increase (R = –0,46, p = 0,06) as well as with clinical effect of therapy improvement of (R = –0,45, p = 0,04). There were no statistical changes in the level of the BAFF factor in patients with HCQ. After GC treatment a decrease in the synthesis of serum IgA (p = 0,01) as well as trend to decline of B-cells number (p = 0,07) were determined, while in patients treated with RAASIs a significant increase in IgE production (p = 0,05) and tendency in elevation in BAFF levels (p = 0,06) were observed. Conclusion Immunological changes may be the determining factors in the choice of treatment in IgAN patients.