B-cell Pathology Research Articles

Novel DNA methylome biomarkers associated with adalimumab response in rheumatoid arthritis patients.

Rheumatoid arthritis (RA) patients are currently treated with biological agents mostly aimed at cytokine blockade, such as tumor necrosis factor-alpha (TNFα). Currently, there are no biomarkers to predict therapy response to these agents. Here, we aimed to predict response to adalimumab (ADA) treatment in RA patients using DNA methylation in peripheral blood (PBL). DNA methylation profiling on whole peripheral blood from 92 RA patients before the start of ADA treatment was determined using Illumina HumanMethylationEPIC BeadChip array. After 6 months, treatment response was assessed according to the European Alliance of Associations for Rheumatology (EULAR) criteria for disease activity. Patients were classified as responders (Disease Activity Score in 28 Joints (DAS28) < 3.2 or decrease of 1.2 points) or as non-responders (DAS28 > 5.1 or decrease of less than 0.6 points). Machine learning models were built through stability-selected gradient boosting to predict response prior to ADA treatment with predictor DNA methylation markers. Of the 94 RA patients, we classified 49 and 43 patients as responders and non-responders, respectively. We were capable of differentiating responders from non-responders with a high performance (area under the curve (AUC) 0.76) using a panel of 27 CpGs. These classifier CpGs are annotated to genes involved in immunological and pathophysiological pathways related to RA such as T-cell signaling, B-cell pathology, and angiogenesis. Our findings indicate that the DNA methylome of PBL provides discriminative capabilities in discerning responders and non-responders to ADA treatment and may therefore serve as a tool for therapy prediction.

Genetic Analyses of Contributions of Viral Interleukin-6 Interactions and Signaling to Human Herpesvirus 8 Productive Replication.

Human herpesvirus 8 (HHV-8) viral interleukin-6 (vIL-6) is a cytokine that is poorly secreted and localized largely to the endoplasmic reticulum (ER). It has been implicated, along with other HHV-8 proinflammatory and/or angiogenic viral proteins, in HHV-8-associated Kaposi's sarcoma, primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), in addition to an MCD-related disorder involving systemic elevation of proinflammatory cytokines, including vIL-6 and human IL-6 (hIL-6). In these diseases, lytic (productive) replication, in addition to viral latency, is believed to play a critical role. Proreplication activity of vIL-6 has been identified experimentally in PEL and endothelial cells, but the relative contributions of different vIL-6 interactions have not been established. Productive interactions of vIL-6 with the IL-6 signal transducer, gp130, can occur within the ER, but vIL-6 also interacts in the ER with a nonsignaling receptor called vitamin K epoxide reductase complex subunit 1 variant 2 (VKORC1v2), calnexin, and VKORC1v2- and calnexin-associated proteins UDP-glucose:glycoprotein glucosyltransferase 1 (UGGT1) and glucosidase II (GlucII). Here, we report the systematic characterization of interaction-altered vIL-6 variants and the lytic phenotypes of recombinant viruses expressing selected variants. Our data identify the critical importance of vIL-6 and its ER-localized activity via gp130 to productive replication in inducible SLK (epithelial) cells, absence of detectable involvement of vIL-6 interactions with VKORC1v2, GlucII, or UGGT1, and the insufficiency and lack of direct contributory effects of extracellular signaling by vIL-6 or hIL-6. These findings, obtained through genetics-based approaches, complement and extend previous analyses of vIL-6 activity.IMPORTANCE Human herpesvirus 8 (HHV-8)-encoded viral interleukin-6 (vIL-6) was the first viral IL-6 homologue to be identified. Experimental and clinical evidence suggests that vIL-6 is important for the onset and/or progression of HHV-8-associated endothelial-cell and B-cell pathologies, including AIDS-associated Kaposi's sarcoma and multicentric Castleman's disease. The protein is unusual in its poor secretion from cells and its intracellular activity; it interacts, directly or indirectly, with a number of proteins beyond the IL-6 signal transducer, gp130, and can mediate activities through these interactions in the endoplasmic reticulum. Here, we report the characterization with respect to protein interactions and signal-transducing activity of a panel of vIL-6 variants and utilization of HHV-8 mutant viruses expressing selected variants in phenotypic analyses. Our findings establish the importance of vIL-6 in HHV-8 productive replication and the contributions of individual vIL-6-protein interactions to HHV-8 lytic biology. This work furthers understanding of the biological significance of vIL-6 and its unique intracellular interactions.

Coexistence of B-Cell Dyscrasia with Large Granular Lymphocytic Leukemia

Large granular lymphocytic leukemia (LGLL) is an indolent disease and often associated with autoimmune disorders such as rheumatoid arthritis. The association of humoral immune disorders resulting from abnormal B cell activity, may affect original LGLL pathogenesis, clinical presentation and management through modifying disease presentation, progression and/ or resistance to standard care. Coexistence of T cell LGL leukemia with B cell abnormalities has previously been identified in the literature although described in sporadic case reports. However, no large case series or cohorts have been collected so far to study the frequency of the B-cell dyscrasia (BCD) associated with LGLL and describe clinical/ hematological findings in patients with this co-association. Here, we conducted a retrospective review of patients diagnosed with LGL leukemia at The Cleveland Clinic Foundation to search for any associated BCDs. We then classified our population into 2 groups: LGLL with BCD vs. LGLL without BCD, and comprehensively compared them for baseline, clinical and molecular characteristics. A total of 244 T-LGL patients were collected and studied. All cases were uniformly diagnosed with LGLL if 3 out of 4 following criteria were fulfilled, including: 1) LGL count &gt;500/µL in blood for more than 6 months; 2) presence of abnormal CTLs expressing CD3, CD8 and CD57 by flow cytometry; 3) preferential usage of a TCR Vβ family by flow cytometry; 4) TCR gene rearrangement by PCR. Molecular studies including targeted deep sequencing for STAT3mutations were performed. Bone marrow biopsy results were reviewed to exclude other conditions. Endpoints of the study were death or lost to follow up. In our cohort, we found a frequent manifestation of humoral immune system abnormalities. We identified coexisting BCD in 45% (109/ 244) of LGLL patients, of whom 28 (11.2%) had monoclonal gammopathy of unknown significance (MGUS), and 13 (5.2%) had chronic lymphocytic leukemia (CLL/SLL). Six LGLL patients had multiple myeloma (2.4%). Moreover, polyclonal hypergammaglobulinemia (n=28, 11.2%) or hypogammaglobulinemia (n=14, 5.6%) was reported in 42 LGLL-patients (16.8%). The frequency of other disorders of B-cell origin was also examined. The total incidence of B-cell abnormalities in our LGLL cohort was 45%. Indeed an heterogeneous appearance of other B-cell disorders was observed including mantle cell lymphoma (n=2), DLBCL (n=6), marginal zone lymphoma (n=3), Waldenstrom's macroglobulinemia (n=1), Burkitt's lymphoma (n=1), indolent lymphoma (n=1), Hodgkin's lymphoma (n=1), non-Hodgkin's lymphoma (n=3), neck lymphoma (n=1), and smoldering myeloma (n=2). Patient with LGLL-BCD were older as compared to the ones without (median age: 62 vs. 63 years; ≥60 years: 57% vs. 69%, respectively), although the difference was not statistically significant (P=0.07). Gender was equally distributed (male: 54%, n=132; female: 46%, n=112) in patients who developed BCD. Conventional cytogenetics showed that patients without BCD were more often associated with abnormal cytogenetics (24%, n=9) as compared to LGLL-BCD (9%, n=5). Interestingly, BCD was found in 55 men and 54 women in whom only 6 patients had NK-LGLL while the remaining (n=103 patients) had T-LGLL suggesting a higher association with LGLL of T- rather than of NK-cell origin. Leukopenia was observed in 25/109 patients, with average absolute lymphocytes of 4.18 k/µL and LGL count of 2333 k/µL. Blood count showed: neutropenia in 44, anemia in 65, and thrombocytopenia in 29 out of 109 LGLL patients with BCD. TCR rearrangements were seen in 74 while somatic STAT3 mutations were observed in 37 LGLL patients while more enriched (44%, n=52) in LGLL without BCD. The association of other autoimmune conditions e.g., rheumatoid arthritis, was not different between the two groups (15% vs. 16% in LGLL with BCD vs. without; P=0.8). In sum, our investigation shows that BCD were frequent in LGLL and coexisted in 45% of the patients, commonly in the form of MGUS, and/ or hypergamaglobulinemia. Perhaps, the co-association of B-cell pathology with LGLL suggests that the two diseases either share pathogenetic driving mechanisms to enhance both B cells and T cells clones or that immunological dysfunction in setting of B cell dyscrasia could trigger/potentiate LGL expansion and/or transformation in this context. Disclosures No relevant conflicts of interest to declare.

Restricted, canonical, stereotyped and convergent immunoglobulin responses.

It is becoming evident that B-cell responses to particular epitopes or in particular contexts can be highly convergent at the molecular level. That is, depending on the epitope targeted, persons of diverse genetic backgrounds and immunological histories can use highly similar, stereotyped B-cell receptors (BCRs) for a particular response. In some cases, multiple people with immunity to a particular epitope or with a type of B-cell neoplasia will elicit antibodies encoded by essentially identical immunoglobulin gene rearrangements. In other cases, particular VH genes encode antibodies important for immunity against pathogens such as influenza and HIV. It appears that the conserved antibody structures driving these stereotyped responses are highly limited and selected. There are interesting and important convergences in the types of stereotyped BCRs induced in conditions of immunity and B-cell-related pathology such as cancer and autoimmunity. By characterizing and understanding stereotyped B-cell responses, novel approaches to B-cell immunity and in understanding the underlying causes of B-cell pathology may be discovered. In this paper, we will review stereotyped BCR responses in various contexts of B-cell immunity and pathology.

PTU-110 What impact do hcv infection and subclinical cryoglobulinaemia have on the b cell repertoire?

Introduction In addition to causing liver injury, hepatitis C virus (HCV) is closely associated with clonal B-cell pathologies such as cryogloglobulinaemia. 1 The virus is also capable of evading control by antibody responses. 2 Understanding the mechanisms by which HCV resists clearance by the adaptive immune system is important in vaccine design. We hypothesised that HCV infection may restrict the B-cell repertoire, predisposing to clonal B-cell disorders and contributing to impaired ability to mount an effective anti-viral antibody response. We aimed to explore this by determining: Any differences in B-cell Receptor (BCR) characteristics between HCV-infected individuals with and without cryoglobulinaemia. Any functional differences in viral neutralising ability associated with subclinical cryoglobulinaemia. Method Patients chronically infected with either genotype 1 (G1) or genotype 3 (G3) HCV were prospectively recruited in addition to healthy controls (HC). None had a prior diagnosis of cryoglobulinaemia. Patient serum was tested for presence of cryoprecipitates. Purified IgG from patient serum was tested for ability to prevent infection of cultured cells by a panel of HCV envelope-coated ‘pseudoparticles’. For a subset of HCV-infected patients and HC, RNA was extracted from PBMCs and cDNA libraries generated. BCR genes were amplified and underwent 454 sequencing. Sequences were analysed for overall diversity, clonality and specific gene usage using an in-house programme. Results 75 HCV-infected patients (36 G1, 39 G3) were recruited. Of the HCV-infected individuals, 28% (21/75) had detectable cryoprecipitates. There was no association between presence of cryoglobulins and functional antibody responses (p = 0.77). BCR sequences were analysed for 6 cryoglobulin positive, 6 cryoglobulin negative and 6 HC. There was no difference in overall BCR diversity between the groups. Cryoglobulin positive individuals showed reduced expression of IGHV 1–8 (p = 0.004). The antigen binding CDR3 region was longer in cryoglobulinaemic individuals than HC (p = 0.028). Conclusion Our data suggest that asymptomatic cyoglobulinaemic antibodies are common in chronic HCV infection. While these are not associated with an obvious deficit in antibody function or BCR diversity, next generation sequencing has revealed potentially important differences in their B-cell receptor populations. These novel findings and their functional implications require further analysis. Disclosure of interest None Declared. References Charles ED, et al . Blood 2008;111:1344–1356 Edwards VC, et al . J Gen Virol. 2012;93:1–19

Characterization of B cells in muscle-specific kinase antibody myasthenia gravis.

Objective:To characterize B-cell subsets in patients with muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG).Methods:In accordance with Human Immunology Project Consortium guidelines, we performed polychromatic flow cytometry and ELISA assays in peripheral blood samples from 18 patients with MuSK MG and 9 healthy controls. To complement a B-cell phenotype assay that evaluated maturational subsets, we measured B10 cell percentages, plasma B cell–activating factor (BAFF) levels, and MuSK antibody titers. Immunologic variables were compared with healthy controls and clinical outcome measures.Results:As expected, patients treated with rituximab had high percentages of transitional B cells and plasmablasts and thus were excluded from subsequent analysis. The remaining patients with MuSK MG and controls had similar percentages of total B cells and naïve, memory, isotype-switched, plasmablast, and transitional B-cell subsets. However, patients with MuSK MG had higher BAFF levels and lower percentages of B10 cells. In addition, we observed an increase in MuSK antibody levels with more severe disease.Conclusions:We found prominent B-cell pathology in the distinct form of MG with MuSK autoantibodies. Increased BAFF levels have been described in other autoimmune diseases, including acetylcholine receptor antibody–positive MG. This finding suggests a role for BAFF in the survival of B cells in MuSK MG, which has important therapeutic implications. B10 cells, a recently described rare regulatory B-cell subset that potently blocks Th1 and Th17 responses, were reduced, which suggests a potential mechanism for the breakdown in immune tolerance in patients with MuSK MG.

ADAM10 releases the immunoregulator soluble TACI — A novel biomarker for B-cell pathologies

The BAFF-APRIL system is critically involved in controlling B-cell homeostasis. Here the receptor TACI has ambiguous functions: while humans with TACI mutations present with antibody deficiency syndroms, TACI−/− mice develop autoimmunity and lymphoproliferation. Generation of soluble receptors is a common feature in the regulation of inflammatory processes. In our study we identify soluble TACI (sTACI) and characterize the structure and function of this soluble receptor.

Targeting IRF5 inhibition in human B cells: identification of new functional roles that implicate IRF5 in systemic lupus erythematosus B-cell pathology

Targeting IRF5 inhibition in human B cells: identification of new functional roles that implicate IRF5 in systemic lupus erythematosus B-cell pathology

The use of humoral responses as a marker of CMV burden in HIV patients on ART requires consideration of T-cell recovery and persistent B-cell activation.

Objectives. Elevated humoral responses to cytomegalovirus (CMV) associate with increased risk of cardiovascular disease (CVD) in HIV patients on antiretroviral therapy (ART). To better understand the persistence of CMV humoral responses in relation to CVD, we determined trends in CMV antibody levels over the first 10 years on ART. Design. We describe longitudinal analyses of plasma from 13 HIV patients commencing ART with <210 CD4 T-cells/µL and 27 controls. Antibodies reactive with CMV (fibroblast lysate, gB and IE-1 antigens), EBV-VCA, and HIVgp41 were quantitated. B-cell activation was assessed via total IgG and sBAFF. Inflammation was assessed via sTNF-RI and sCD14. Results. Amongst CMV seropositive HIV patients, levels of antibody reactive with CMV (P = 0.03) and EBV-VCA (P = 0.02) peaked after 1 year on ART. Levels of total IgG, sCD14, and sTNF-RI declined to approximate those in controls after 10 years, but sBAFF (P = 0.0002), EBV-VCA (P = 0.001), and CMV (P = 0.0004) antibodies remained elevated. A strong correlation between sBAFF and CMVgB antibody was seen at 10 years (R = 0.93, P = 0.0009) and verified in a second cohort. Conclusions. CMV antibody titres peak on ART and remain high. A correlation between CMV antibody and sBAFF suggests a role for HIV-induced B-cell pathology that may affect its use as a marker of CMV burden.

Selective killing of Kaposi's sarcoma-associated herpesvirus lytically infected cells with a recombinant immunotoxin targeting the viral gpK8.1A envelope glycoprotein

Kaposi sarcoma-associated herpesvirus (KSHV, human herpesvirus 8) is etiologically associated with three neoplastic syndromes: Kaposi sarcoma and the uncommon HIV-associated B-cell lymphoproliferative disorders primary effusion lymphoma and multicentric Castleman disease. The incidence of the latter B-cell pathology has been increasing in spite of antiretroviral therapy; its association with lytic virus replication has prompted interest in therapeutic strategies aimed at this phase of the virus life cycle. We designed and expressed a recombinant immunotoxin (2014-PE38) targeting the gpK8.1A viral glycoprotein expressed on the surface of the virion and infected cells. We show that this immunotoxin selectively kills KSHV-infected cells in dose-dependent fashion, resulting in major reductions of infectious virus release. The immunotoxin and ganciclovir, an inhibitor of viral DNA replication, showed marked reciprocal potentiation of antiviral activities. These results suggest that the immunotoxin, alone or in combination, may represent a new approach to treat diseases associated with KSHV lytic replication.

B-cell numbers and phenotype at clinical relapse following rituximab therapy differ in SLE patients according to anti-dsDNA antibody levels

Objectives. To correlate the kinetics of B-cell repopulation with relapse after B-cell depletion therapy in SLE patients and address whether variation in relapse rate, B-cell numbers and phenotype are related to anti-dsDNA antibody levels.Methods. Sixty-one patients with refractory SLE were treated with a standard rituximab regimen. Clinical and serological measures of disease activity and B-cell numbers were assessed. B-cell phenotype was examined in a subgroup of patients by flow cytometry.Results. Disease relapse was substantially delayed beyond B-cell repopulation, and early relapse was associated with a faster rate of repopulation. At relapse, B-cell numbers were significantly lower than at baseline in patients with high anti-dsDNA antibody levels (>100 IU/ml) but not in patients with low anti-dsDNA antibody levels. Of the patients with high anti-dsDNA antibodies at baseline, levels fell significantly only in those patients who remained in remission after repopulation. Relapse with high anti-dsDNA antibody levels was associated with an increased percentage of IgD−CD27hi plasmablasts, whereas relapse with low anti-dsDNA antibody levels was accompanied by an increased percentage of IgD−CD27− B cells.Conclusion. Anti-dsDNA antibody levels distinguished two patient groups, which differ in their B-cell number and phenotype at relapse following rituximab, and suggest that different B-cell pathologies exist in SLE. The data imply that B-cell numbers should be kept very low for a sustained period in patients with high dsDNA binding, therefore justifying a more aggressive regimen.

Evidence for functional trace amine associated receptor-1 in normal and malignant B cells

Following the observation that dopaminergic components are present in normal and malignant B cells, we now provide evidence that they additionally express the functionally related trace amine-associated receptor-1 (TAAR1). Immunodetectable TAAR1 was found in lines derived from a broad range of B-cell malignancy; and in tonsillar B cells, particularly when activated. L3055 Burkitt's lymphoma cells were shown to respond to prototypical TAAR1 agonists in cytotoxicity assays with features of apoptotic death evident; normal B cells were somewhat less sensitive to the agonists. These data raise the possibility that TAAR1 may have therapeutic relevance to leukemia, lymphoma, and wider B-cell pathologies.

Specific effects exerted by B‐lymphoproliferative diseases on peripheral T‐lymphocyte protein expression

A proteomic approach was applied to study the protein expression profile of peripheral T-cells derived from patients at the onset of different B-lymphoproliferative diseases, because a rising interest in specific actions played by T-cells in such pathologies has emerged. Decreased levels of profilin-1 and cofilin-1 and increased levels of coronin1A and prohibitin were found in patients, compared with healthy controls. The protein-protein interaction network of these proteins was studied using a web-based bioinformatics tool, highlighting the actin cytoskeleton regulation as the main biological process involved in peripheral T-cells of such patients. Unsupervised cluster analysis of protein expression data shows that the recorded alteration of T-cell proteome was specifically induced by B-cell pathologies.

Active Surveillance Strategies Have Neither Clinical or Survival Benefit Following High-Dose Chemotherapy and Progenitor Cell Rescue in Follicular Lymphoma.

Introduction: Annual surveillance CT scans and bone marrow (BM) biopsies are frequently performed in follow-up of patients (pts.) receiving high-dose therapy (HDT) with autologous stem cell rescue for recurrent follicular lymphoma (FL). The impact of this active surveillance strategy on the outcome of a homogeneously treated population was analysed.Methods: Ninety-nine consecutive pts. who received HDT (cyclophosphamide and total body irradiation) with autologous stem cell rescue for recurrent FL at St Bartholomew's Hospital between February 1986 and October 1991 were included. The surveillance policy at that time included an annual CT scan and BM biopsy. Time to relapse, time to next treatment and overall survival (OS) from the time of HDT were calculated and compared, according to whether disease progression had been diagnosed on the basis of surveillance investigations or on clinical grounds. Seventy out of 99 pts. are evaluable, the remainder are not, due to: relapse or death within one year of HDT (20 pts.), follow-up elsewhere (8 pts.) or patient's wishes (1 pt.). 86% of pts. who commenced surveillance actually had annual CT scans and BM biopsies until disease progression or death.Results: After a median follow-up of 16.7 years (y), progression was documented in 35/70 pts. (50%). It was detected by surveillance alone in 14 pts. and clinically, in 21 pts. (40% and 60% of all recurrences, respectively). The commonest presentations of clinical relapse were peripheral lymphadenopathy (62%), pain (19%) and B-symptoms (10%). Surveillance relapses were diagnosed on the basis of a CT scan in 43% of pts., a BM biopsy in 36% and both in 14%. The median time from HDT to relapse was 2y for pts. with a clinically detected relapse and 2.8y in those with a surveillance relapse but the difference was not statistically significant (p=0.2). Treatment was started immediately in 13 of 21 pts. (62%) with a clinical relapse, contrasting with only one of 14 pts. (7%) diagnosed on surveillance. The main reasons for starting treatment were biopsy-proven transformation to diffuse large B-cell pathology (8 of the pts. with a clinical relapse and one with a surveillance relapse) and rapidly progressing lymphadenopathy. All other pts. were managed expectantly (observation). The median time from HDT until clinical progression was 8.2y in the 14 pts. whose relapse was detected by surveillance; 4 of the 14 have not yet developed signs or symptoms of recurrence. Thus, the clinical relapse rate in the cohort under surveillance is 44% (31/70). Six of the pts. with a surveillance relapse have still not started treatment (median follow-up: 13.8y; range: 1.9y–22.1y). Only 2 of the 21 pts. with a clinically detected relapse have not started treatment after 5.6y and 14.3y of follow-up. Thus, the median time from HDT to next treatment was significantly shorter for pts. with a clinical relapse (3.6y) in comparison with those in whom the recurrence was diagnosed by surveillance investigations (11.3y; p=0.0004). Median OS was 5.6y and 13.4y for pts. with a clinical and a surveillance relapse, respectively (p=0.03).Conclusions: In pts. with FL, relapses diagnosed on the basis of surveillance investigations usually have an indolent course and frequently do not require treatment. In contrast, clinically detected relapses have a more aggressive clinical course and treatment is initiated immediately in the majority of cases. Thus, annual surveillance investigations do not help to identify pts. that require treatment and do not improve the outcome of this population. They should therefore be abandoned. Time to relapse based on data from pts. on annual surveillance should be interpreted with caution because of the poor correlation with time to next treatment and OS.

In vivo leukocyte tropism of bovine leukemia virus in sheep and cattle

Bovine leukemia virus (BLV), an oncovirus related to human T-cell leukemia virus type I, causes a B-cell lymphoproliferative syndrome in cattle, leading to an inversion of the T-cell/B-cell ratio and, more rarely, to a B-cell lymphosarcoma. Sheep are highly sensitive to BLV experimental infection and develop B-cell pathologies similar to those in cattle in 90% of the cases. BLV tropism for B cells has been well documented, but the infection of other cell populations may also be involved in the BLV-induced lymphoproliferative syndrome. We thus looked for BLV provirus in other leukocyte populations in sheep and cattle by using PCR. We found that while B cells harbor the highest proviral load, CD8+ T cells, monocytes, and granulocytes, but not CD4+ T cells, also bear BLV provirus. As previously described, we found that persistent lymphocytosis in cows is characterized by an expansion of the CD5+ B-cell subpopulation but we did not confirm this observation in sheep in which the expanded B-cell population expressed the CD11b marker. Nevertheless, BLV could be detected both in bovine CD5+ and CD5- B cells and in sheep CD11b+ and CD11b- B cells, indicating that the restricted BLV tropism for a specific B-cell subpopulation cannot explain its expansion encountered in BLV infection. Altogether, this work shows that BLV tropism in leukocytes is wider than previously thought. These results lead the way to further studies of cellular interactions among B cells and other leukocytes that may intervene in the development of the lymphoproliferative syndrome induced by BLV infection.

Immunofluorescent and ultrastructural analysis of plasma cell degeneration in the chicken Harder's gland

In this study we describe some aspects of plasma cell degeneration in the chicken Harder's gland. The immunofluorescent patterns of cytoplasmic immunoglobulin (cIg) localization have been studied in relation to the ultrastructure of maturing and degenerating B cells. It appears that Russell body formation through the accumulation of Ig within the cisternae of the rough endoplasmic (RER) does not represent the only mechanism for the formation of cytoplasmic vacuoles. Mitochondrial swelling and disruption or dilation of Golgi cisternae, often preceding alterations of the RER, may be the origin of some vacuoles. It also appears that, in the Harder's gland, degeneration may occur not only in mature plasma cells but also in maturing B cells at a stage when only clusters of polyribosomes are found in the cytoplasm and no RER is yet developed. These observations are relevant to some immunofluorescence and ultrastructural patterns observed in human B-cell pathology.