Delayed acquisition of somatic hypermutations in repopulated IGD+CD27+ memory B cell receptors after rituximab treatment

Microfluidic antibody profiling after repeated SARS-CoV-2 vaccination links antibody affinity and concentration to impaired immunity and variant escape in patients on anti-CD20 therapy

Background

Patients with autoimmune/inflammatory conditions on anti-CD20 therapies, such as rituximab, have suboptimal humoral responses to vaccination and are vulnerable to poorer clinical outcomes following SARS-CoV-2 infection. We aimed to examine how the fundamental parameters of antibody responses, namely, affinity and concentration, shape the quality of humoral immunity after vaccination in these patients.

Methods

We performed in-depth antibody characterisation in sera collected 4 to 6 weeks after each of three vaccine doses to wild-type (WT) SARS-CoV-2 in rituximab-treated primary vasculitis patients (n = 14) using Luminex and pseudovirus neutralisation assays, whereas we used a novel microfluidic-based immunoassay to quantify polyclonal antibody affinity and concentration against both WT and Omicron (B.1.1.529) variants. We performed comparative antibody profiling at equivalent timepoints in healthy individuals after three antigenic exposures to WT SARS-CoV-2 (one infection and two vaccinations; n = 15) and in convalescent patients after WT SARS-CoV-2 infection (n = 30).

Results

Rituximab-treated patients had lower antibody levels and neutralisation titres against both WT and Omicron SARS-CoV-2 variants compared to healthy individuals. Neutralisation capacity was weaker against Omicron versus WT both in rituximab-treated patients and in healthy individuals. In the rituximab cohort, this was driven by lower antibody affinity against Omicron versus WT [median (range) KD: 21.6 (9.7-38.8) nM vs. 4.6 (2.3-44.8) nM, p = 0.0004]. By contrast, healthy individuals with hybrid immunity produced a broader antibody response, a subset of which recognised Omicron with higher affinity than antibodies in rituximab-treated patients [median (range) KD: 1.05 (0.45-1.84) nM vs. 20.25 (13.2-38.8) nM, p = 0.0002], underpinning the stronger serum neutralisation capacity against Omicron in the former group. Rituximab-treated patients had similar anti-WT antibody levels and neutralisation titres to unvaccinated convalescent individuals, despite two more exposures to SARS-CoV-2 antigen. Temporal profiling of the antibody response showed evidence of affinity maturation in healthy convalescent patients after a single SARS-CoV-2 infection, which was not observed in rituximab-treated patients, despite repeated vaccination.

Discussion

Our results enrich previous observations of impaired humoral immune responses to SARS-CoV-2 in rituximab-treated patients and highlight the significance of quantitative assessment of serum antibody affinity and concentration in monitoring anti-viral immunity, viral escape, and the evolution of the humoral response.

Long-term Rituximab Therapy in Adult Patients with Idiopathic Nephrotic Syndrome

Patients with refractory idiopathic nephrotic syndrome (INS) are at risk of infections, renal failure, and the inherent side effects of immunosuppressive therapy. In the present study, we investigated the efficacy of yearly rituximab therapy in adult patients with this syndrome over 5-10 years. In the minimal change disease group, 14 of the 15 patients had complete remission (CR) and one had partial remission (PR). Of those who achieved CR, eight patients did not require rituximab 4 years later. The patient with PR was treated in the same way as those with focal segmental glomerulosclerosis (FSGS) group and remained stable by the end of the study. In the FSGS group, rituximab therapy resulted in the amelioration of INS in nine patients, although two were non-responders (NR) and developed end-stage renal disease (ESRD). In the membranous glomerulopathy group, 36 patients had CR but two were NR and developed ESRD. Twenty (55%) of those did not require treatment after 4 years, whereas the rest maintained CR with yearly rituximab. Nine women received rituximab after the third month of pregnancy without significant adverse effects on the fetus or subsequent conception. In conclusion, rituximab is a safe, practical, and effective long-term therapy for adult patients in these three groups of INS.

Rituximab Therapy for Primary Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a systemic autoimmune diseases of the connective tissues, characteristic of the presentation of keratoconjunctivitis sicca and xerostomia. A cardinal pathogenetic feature of SS is B-cell hyperactivity, which has invited efforts on optimal B-cell targeted therapy, whereas conventional corticosteroids and disease-modifying antirheumatic drugs (DMARDs) are restricted to symptomatic relief. As per the first EULAR recommendation for pSS patients published in 2020, regimens with monoclonal antibodies targeting B cells may be initiated in patients with severe, refractory systemic disease, notably rituximab (RTX), a mouse-derived monoclonal antibody that targets CD20 antigen and contributes to B-cell depletion. Nonetheless, the data available from clinical trials with RTX are often controversial. Despite the lack of promising results from two large RCTs, several positive clinical efficacies were demonstrated. This current review addressed the efficacy and safety of clinical trials available and elucidated the potential of RTX on the immune system, especially B and T cells. Furthermore, plausible explanations for the discrepancy in clinical data were also presented.

Vascular Inflammation in Cardiovascular Disease: Is Immune System Protective or Bystander?

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Chronic atherosclerosis induced vascular inflammation and perturbation of lipid metabolism is believed to be a major cause of CVD. Interplay of innate and adaptive Immune system has been interwined with various risk factors associated with the initiation and progression of atherosclerosis in CVD. A large body of evidence indicates a correlation between immunity and atherosclerosis. Retention of plasma lipoproteins in arterial subendothelial wall triggers the T helper type 1 (Th1) cells and monocyte-derived macrophages to form atherosclerotic plaques. In the present review, we will discuss the pathogenesis of CVD in relation to atherosclerosis with a particular focus on pro-atherogenic role of immune cells. Recent findings have also suggested anti-atherogenic roles of different B cell subsets. Therapeutic approaches to target atherosclerosis risk factors have reduced the mortality, but a need exists for the novel therapies to treat arterial vascular inflammation. These insights into the immune pathogenesis of atherosclerosis can lead to new targeted therapeutics to abate cardiovascular mortality and morbidity.

Double-negative (DN) B cells: an under-recognized effector memory B cell subset in autoimmunity

Human B cells could be divided into four classical subsets based on CD27 and immunoglobulin (Ig)D expression. Distinct from the other three well-studied subsets, CD27^- IgD^- B cells, also termed as double-negative (DN) B cells, have long been neglected. However, in recent years emerging evidence shows that DN B cells are unique memory B cells with important functions. They are expanded in a variety of diseases, especially in autoimmune diseases, contributing to the disease pathogenesis. Here, we briefly review the studies on DN B cells, including their origins, characteristics, subsets and roles in diseases, to try to bring new insights into this under-recognized B cell subset.

Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles

Measles is a disease caused by the highly infectious measles virus (MeV) that results in both viremia and lymphopenia. Lymphocyte counts recover shortly after the disappearance of measles-associated rash, but immunosuppression can persist for months to years after infection, resulting in increased incidence of secondary infections. Animal models and in vitro studies have proposed various immunological factors underlying this prolonged immune impairment, but the precise mechanisms operating in humans are unknown. Using B cell receptor (BCR) sequencing of human peripheral blood lymphocytes before and after MeV infection, we identified two immunological consequences from measles underlying immunosuppression: (i) incomplete reconstitution of the naïve B cell pool leading to immunological immaturity and (ii) compromised immune memory to previously encountered pathogens due to depletion of previously expanded B memory clones. Using a surrogate model of measles in ferrets, we investigated the clinical consequences of morbillivirus infection and demonstrated a depletion of vaccine-acquired immunity to influenza virus, leading to a compromised immune recall response and increased disease severity after secondary influenza virus challenge. Our results show that MeV infection causes changes in naïve and memory B lymphocyte diversity that persist after the resolution of clinical disease and thus contribute to compromised immunity to previous infections or vaccinations. This work highlights the importance of MeV vaccination not only for the control of measles but also for the maintenance of herd immunity to other pathogens, which can be compromised after MeV infection.

Infectious Complications of Biological and Small Molecule Targeted Immunomodulatory Therapies

The past 2 decades have seen a revolution in our approach to therapeutic immunosuppression. We have moved from relying on broadly active traditional medications, such as prednisolone or methotrexate, toward more specific agents that often target a single receptor, cytokine, or cell type, using monoclonal antibodies, fusion proteins, or targeted small molecules. This change has transformed the treatment of many conditions, including rheumatoid arthritis, cancers, asthma, and inflammatory bowel disease, but along with the benefits have come risks. Contrary to the hope that these more specific agents would have minimal and predictable infectious sequelae, infectious complications have emerged as a major stumbling block for many of these agents. Furthermore, the growing number and complexity of available biologic agents makes it difficult for clinicians to maintain current knowledge, and most review articles focus on a particular target disease or class of agent. In this article, we review the current state of knowledge about infectious complications of biologic and small molecule immunomodulatory agents, aiming to create a single resource relevant to a broad range of clinicians and researchers. For each of 19 classes of agent, we discuss the mechanism of action, the risk and types of infectious complications, and recommendations for prevention of infection.

Current Developments in the Immunology of Psoriasis

Psoriasis is a frequent inflammatory skin disease. Fundamental research on the pathogenesis of psoriasis has substantially increased our understanding of skin immunology, which has helped to introduce innovative and highly effective therapies. Psoriasis is a largely T lymphocyte-mediated disease in which activation of innate immune cells and pathogenic T cells result in skin inflammation and hyperproliferation of keratinocytes. B cells have thus far largely been neglected regarding their role for the pathogenesis of psoriasis. However, recent data shed light on their role in inflammatory skin diseases. Interestingly, interleukin (IL)-10-producing regulatory B cells have been assumed to ameliorate psoriasis. In this review, we will discuss the development of disease, pathogenicity, and current developments in therapeutic options. We describe different roles of T cells, B cells, and cytokines for the immunopathology and disease course of psoriasis.

Post-rituximab immunoglobulin M (IgM) hypogammaglobulinemia

Rituximab is a B cell depleting monoclonal antibody that targets the B cell-specific cell surface antigen CD20 and is currently used to treat several autoimmune diseases. The elimination of mature CD20-positive B lymphocytes committed to differentiate into autoantibody-producing plasma cells is considered to be the major effect of rituximab, that makes it a beneficial biological agent in treating autoimmune diseases. Hypogammaglobulinemia has been reported after rituximab therapy in patients with lymphoma and rheumatoid arthritis. Similar data are scarce for other autoimmune diseases. Low immunoglobulin G (IgG) or hypogammaglobulinemia has attracted the most attention because of its significant role in protective immunity. However, the incidence and clinical implications of low immunoglobulin M (IgM) or hypogammaglobulinemia have not been studied in detail. This review will focus on the frequency and the clinical concerns of low IgM levels that result as a consequence of the administration of rituximab. The etiopathogenic mechanisms underlying post-rituximab IgM hypogammaglobulinemia and its implications are presented. The long-term consequences, if any, are not known or documented. Multiple factors may be involved in whether IgG or IgM decreases secondary to rituximab therapy. It is possible that the autoimmune disease itself may be one of the important factors. The dose, frequency and number of infusions appear to be important variables. Post-rituximab therapy immunoglobulin levels return to normal. During this process. IgM levels take a longer time to return to normal levels when compared to IgG or other immunoglobulins. IgM deficiency persists after B cell repopulation to normal levels has occurred. Laboratory animals and humans deficient in IgM can have multiple infections. Specific pharmacologic agents or biologic therapy that address and resolve IgM deficiency are currently unavailable. If the clinical situation so warrants, then prophylactic antibiotics may be indicated and perhaps helpful. Research in this iatrogenic phenomenon will provide a better understanding of not only the biology of IgM, but also the factor(s) that control its production and regulation, besides its influence if any, on rituximab therapy.

Oral Lichenoid Reaction: An Uncommon Side Effect of Rituximab

Oral lichenoid reactions (OLR) can be caused by systemic drug exposure. To the best of our knowledge, this is the second report describing a case of OLR induced by rituximab administration in a patient with a diagnosis of non-Hodgkin B-cell lymphoma. After 5 doses of rituximab, a typical pattern of OLP was identified with bilateral and symmetrical lesions on the buccal mucosa and on the right lingual margin. This temporal relationship suggested a probable association between oral lesions and drug therapy. The clinical diagnosis of a rituximab-induced OLR was confirmed by an incisional biopsy reporting a histopathological result of lichenoid mucositis consistent with oral lichen planus. Because of the increasing use of rituximab, it is necessary to know and recognize this uncommon side effect.

Reversing Autoimmunity Combination of Rituximab and Intravenous Immunoglobulin

In this concept paper, the authors present a unique and novel protocol to treat autoimmune diseases that may have the potential to reverse autoimmunity. It uses a combination of B cell depletion therapy (BDT), specifically rituximab (RTX) and intravenous immunoglobulin (IVIg), based on a specifically designed protocol (Ahmed Protocol). Twelve infusions of RTX are given in 6–14 months. Once the CD20⁺ B cells are depleted from the peripheral blood, IVIg is given monthly until B cells repopulation occurs. Six additional cycles are given to end the protocol. During the stages of B cell depletion, repopulation and after clinical recovery, IVIg is continued. Along with clinical recovery, significant reduction and eventual disappearance of pathogenic autoantibody occurs. Administration of IVIg in the post-clinical period is a crucial part of this protocol. This combination reduces and may eventually significantly eliminates inflammation in the microenvironment and facilitates restoring immune balance. Consequently, the process of autoimmunity and the phenomenon that lead to autoimmune disease are arrested, and a sustained and prolonged disease and drug-free remission is achieved. Data from seven published studies, in which this combination protocol was used, are presented. It is known that BDT does not affect check points. IVIg has functions that mimic checkpoints. Hence, when inflammation is reduced and the microenvironment is favorable, IVIg may restore tolerance. The authors provide relevant information, molecular mechanism of action of BDT, IVIg, autoimmunity, and autoimmune diseases. The focus of the manuscript is providing an explanation, using the current literature, to demonstrate possible pathways, used by the combination of BDT and IVIg in providing sustained, long-term, drug-free remissions of autoimmune diseases, and thus reversing autoimmunity, albeit for the duration of the observation.

B cell phenotypes in patients with rheumatoid arthritis relapsing after rituximab: expression of B cell-activating factor-binding receptors on B cell subsets

Serum levels of B cell-activating factor (BAFF) rise following rituximab (RTX) therapy in patients with rheumatoid arthritis (RA). Initiation of naive B cell return to the periphery and autoreactive B cell expansion leading to relapse after RTX may therefore be linked to interactions between BAFF and BAFF-binding receptors (BBR). Relationships between serum BAFF and BBR expression [(BAFFR, calcium signal modulating cyclophilic ligand interactor (TACI) and B cell maturation antigen (BCMA)] were determined on B cell subsets, defined using immunoglobulin (Ig)D/CD38. Twenty pre-RTX and 18 RA patients relapsing after B cell depletion were included. Results were analysed with respect to timing of relapse up to 7 months after peripheral B cell return (≥ 5 B cells/μl) and to serum BAFF levels. After B cell return, B cell populations from relapsing patients had significantly lower BAFFR⁺ expression compared to HC and pre-RTX patients. The percentage of BAFFR⁺ B cells increased with time after B cell return and was correlated inversely with serum BAFF levels. BAFFR expression remained reduced. The percentage of TACI⁺ memory B cells were lower in RA patients after RTX compared with healthy controls (HC). BCMA expression (% and expression) did not differ between patients and HC. Relapse following B cell return appeared largely independent of the percentage of BAFFR⁺ or percentage of BCMA⁺ B cells or serum BAFF levels. The lower percentage of TACI⁺ memory B cells may reduce inhibitory signalling for B cell differentiation. In patients relapsing at longer periods after B cell return, recovery of the B cell pool was more complete, suggesting that selection or expansion of autoreactive B cells may be needed to precipitate relapse.

Impact of Depleting Therapeutic Monoclonal Antibodies on the Host Adaptive Immunity: A Bonus or a Malus?

Clinical responses to anti-tumor monoclonal antibody (mAb) treatment have been regarded for many years only as a consequence of the ability of mAbs to destroy tumor cells by innate immune effector mechanisms. More recently, it has also been shown that anti-tumor antibodies can induce a long-lasting anti-tumor adaptive immunity, likely responsible for durable clinical responses, a phenomenon that has been termed the vaccinal effect of antibodies. However, some of these anti-tumor antibodies are directed against molecules expressed both by tumor cells and normal immune cells, in particular lymphocytes, and, hence, can also strongly affect the host adaptive immunity. In addition to a delayed recovery of target cells, lymphocyte depleting-mAb treatments can have dramatic consequences on the adaptive immune cell network, its rebound, and its functional capacities. Thus, in this review, we will not only discuss the mAb-induced vaccinal effect that has emerged from experimental preclinical studies and clinical trials but also the multifaceted impact of lymphocytes-depleting therapeutic antibodies on the host adaptive immunity. We will also discuss some of the molecular and cellular mechanisms of action whereby therapeutic mAbs induce a long-term protective anti-tumor effect and the relationship between the mAb-induced vaccinal effect and the immune response against self-antigens.

Cytokine-producing B cells: a translational view on their roles in human and mouse autoimmune diseases

B-cell depletion therapy has beneficial effects in autoimmune diseases. This is only partly explained by an elimination of autoantibodies. How does B-cell depletion improve disease? Here, we review preclinical studies showing that B cells can propagate autoimmune disorders through cytokine production. We also highlight clinical observations indicating the relevance of these B-cell functions in human autoimmunity. Abnormalities in B-cell cytokine production have been observed in rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, and systemic lupus erythematosus. In the first two diseases, B-cell depletion erases these abnormalities, and improves disease progression, suggesting a causative role for defective B-cell cytokine expression in disease pathogenesis. However, in the last two disorders, the pathogenic role of B cells and the effect of B-cell depletion on cytokine-producing B cells remain to be clarified. A better characterization of cytokine-expressing human B-cell subsets, and their modulation by B cell-targeted therapies might help understanding both the successes and failures of current B cell-targeted approaches. This may even lead to the development of novel strategies to deplete or amplify selectively pathogenic or protective subsets, respectively, which might be more effective than global depletion of the B-cell compartment.

CD27-IgD- memory B cells are modulated by in vivo interleukin-6 receptor (IL-6R) blockade in rheumatoid arthritis

Introduction

Enhanced B cell activity, particularly memory B cells have gained interest in evaluating response during therapies with biologics. CD27-IgD- double-negative (DN) B cells lacking the conventional memory marker CD27 are reported to be part of the memory compartment, however, only scarce data is available for rheumatoid arthritis (RA). We therefore focused on DN B cells in RA, studied their isotypes and modulation during interleukin-6 receptor (IL-6R) inhibition by tocilizumab (TCZ).

Methods

DN B cells were phenotypically analyzed from 40 RA patients during TCZ at baseline week 12, week 24 and 1 year. A single B cell polymerase chain reaction (PCR) approach was used to study Ig receptors, V_H gene rearrangements and specific isotypes.

Results

Phenotypic analysis showed a significantly expanded population of DN B cells in RA which contain a heterogeneous mixture of IgG-, IgA- and IgM-expressing cells with a clear dominance of IgG+ cells. DN B cells carry rearranged heavy chain gene sequences with a diversified mutational pattern consistent with memory B cells. In contrast to tumor necrosis factor alpha (TNF-α) inhibition, a significant reduction in mutational frequency of BCR gene rearrangements at week 12, 24 and 1 year (P <0.0001) was observed by in vivo IL-6R inhibition. These changes were observed for all BCR isotypes IgG, IgA and IgM at week 12, 24 and 1 year (P <0.0001). IgA-RF, IgA serum level and IgA+ DN B cells decreased significantly (P <0.05) at week 12 and week 24 during TCZ. Patients with a good European League Against Rheumatism (EULAR) response to TCZ had less DN B cells at baseline as compared to moderate responders (P = 0.006). Univariate logistic regression analysis revealed that the frequency of DN B cells at baseline is inversely correlated to a subsequent good EULAR response (P = 0.024) with an odds ratio of 1.48 (95% confidence interval as 1.05 to 2.06).

Conclusions

In RA, the heterogeneous DN B cell compartment is expanded and dominated by IgG isotype. TCZ can modulate the mutational status of DN Ig isotype receptors over 1 year. Interestingly, the frequency of DN B cells in RA may serve as a baseline predictor of subsequent EULAR response to TCZ.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0580-y) contains supplementary material, which is available to authorized users.

Effect of ATG-F on B-cell reconstitution after hematopoietic stem cell transplantation

Antithymocyte globulin Fresenius (ATG-F) is used before hematopoietic stem cell transplantation to prevent graft rejection and graft-versus-host disease in patients with HLA-matched unrelated donors or mismatched volunteers. However, little is known about the effect of ATG-F on the reconstitution of B-cell subsets. Sixty-seven patients were longitudinally studied at day 15, day 30, and then monthly after hematopoietic stem cell transplantation. Conditioning regimes included ATG-F, which was infused at days 3, 2 and 1 at a dosage of 10 mg/kg/d. Twenty-seven patients received conditioning regimes without ATG. ATG-treated patients showed a significant delay of CD19+ B cells in the early recovery period. The absolute numbers of circulating CD19+ B cells were significantly lower (P < 0.05) up to 5 months post-transplantation compared to non-ATG patients. The recovery of the memory compartment was delayed in both groups and did not reach normal values 1-year post-transplantation. ATG-treated patient showed significantly lower absolute numbers of circulating CD27+ memory B cells in the first-month after transplantation compared to non-ATG patients. In conclusion, treatment with ATG in the conditioning regime of patients undergoing allogeneic hematopoietic stem cell transplantation leads to a significant delay of CD19+ B cells. Thus, ATG seems also to negatively influence B-cell immune reconstitution.

Detection of protein aggregates in brain and cerebrospinal fluid derived from multiple sclerosis patients

Studies of the properties of soluble oligomer species of amyloidogenic proteins, derived from different proteins with little sequence homology, have indicated that they share a common structure and may share similar pathogenic mechanisms. Amyloid β, tau protein, as well as amyloid precursor protein normally associated with Alzheimer’s disease and Parkinson’s disease were found in lesions and plaques of multiple sclerosis patients. The objective of the study is to investigate whether brain and cerebrospinal fluid (CSF) samples derived from multiple sclerosis patients demonstrate the presence of soluble oligomers normally associated with protein-misfolding diseases such as Alzheimer’s disease. We have used anti-oligomer monoclonal antibodies to immunodetect soluble oligomers in CSF and brain tissues derived from multiple sclerosis patients. In this report, we describe the presence of soluble oligomers in the brain tissue and cerebral spinal fluid of multiple sclerosis patients detected with our monoclonal anti-oligomer antibodies with Western blot and Sandwich enzyme-linked immunosorbent assay (sELISA). These results might suggest that protein aggregation plays a role in multiple sclerosis pathogenesis although further and more refined studies are needed to confirm the role of soluble aggregates in multiple sclerosis.

Changes in peripheral blood B cell subsets at diagnosis and after treatment with disease-modifying anti-rheumatic drugs in patients with rheumatoid arthritis: correlation with clinical and laboratory parameters

OBJECTIVE

To assess variation in peripheral blood B lymphocyte subsets in rheumatoid arthritis (RA).

METHODS

B lymphocyte subsets in disease-modifying anti-rheumatic drug (DMARD)-naïve patients with RA (n = 30), patients with RA treated with DMARDs (n = 73) and healthy controls (n = 46) were analyzed by flow cytometry. Total B cells, total memory B cells, immunoglobulin M (IgM) memory B cells, switched memory B cells, non-switched memory B cells, CD21lo B cells, transitional B cells and plasmablasts were measured. Correlation with clinical and laboratory parameters was performed.

RESULTS

Total memory B cells, IgM memory B cells and non-switched memory B cells were reduced in RA patients at diagnosis compared to controls (P < 0.05). In patients with treated RA, there was a further reduction of total B cells, CD21lo cells, transitional B cells and plasmablasts, compared to controls (P < 0.05). The reduction in absolute numbers of total B cells, switched memory B cells, CD21lo cells, transitional B cells and plasmablasts in treated RA patients was significant (P < 0.05) even when compared to the DMARD-naïve patients. Only treatment responders (Disease Activity Score < 3.2) had reduced total B cells and absolute numbers of switched and IgM memory B cells (P < 0.05). In patients requiring leflunomide, total memory B cells, IgM memory B cells, non-switched memory B cells and absolute numbers of switched memory B cells were reduced compared with the remainder of the patient group (P < 0.05).

CONCLUSION

There is reduction of various B cell subsets in RA patients at diagnosis. Treatment with DMARDs leads to further reduction in additional B cell subsets without correction of the abnormalities. Reduction in individual subsets may predict RA patients requiring more intensive therapy.

Risk factors for severe bacterial infections in patients with systemic autoimmune diseases receiving rituximab

The risk of serious bacterial infectious events (SIEs) after an RTX course used in severe and refractory cases of systemic autoimmune diseases (SAID) is well known. Risk factors for SIEs merit investigation. For this case–control study, data were collected in a single centre of internal medicine and included all patients who received rituximab (RTX) for SAID between 2005 and 2011 (rheumatoid arthritis was excluded). Sixty-nine patients with SAID received a total of 87 RTX courses. Thirteen SIEs were reported in 12 patients leading to death in 5 patients. Patients with a history of SIE were significantly older (63.6 ± 18.8 vs 48.8 ± 16.7; p = 0.0091), suffered most frequently of diabetes mellitus (33.3 % vs 5.3 %, p = 0.015), had a lower CD19 count (1.0 ± 1.2/mm³ vs 3.9 ± 7.2/mm³) and had most frequently a prednisone dose >15 mg/day (91.7 % vs 47.7 %) at the start of the first RTX course. The SIE rate was 18.7 per 100 patient-years. At the initiation of the RTX course, risk factors for SIEs were lower IgG levels (OR = 0.87, 95%CI = 0.77–0.99, p = 0.03), lower CD19 count (OR = 0.85, 95%CI = 0.73–1.00) and creatinine clearance ≤ 45 ml/min (OR = 7.78, 95%CI = 1.36–44.38, p = 0.002). Conversely history of pneumococcal vaccination significantly decreased the risk of SIEs (OR = 0.11, 95%CI = 0.03–0.41, p = 0.0009). Concomitant treatment with prednisone at a dose >15 mg/day significantly increased the SIE risk (OR = 8.07, 95%CI = 1.94–33.59, p = 0.0004). SIEs are frequent in SAID treated with RTX, particularly in patients receiving high-dose corticosteroids, in patients with renal insufficiency and in patients with low IgG levels or a low CD19 count.

Rituximab therapy for severe cutaneous leukocytoclastic angiitis refractory to corticosteroids, cellcept and cyclophosphamide

We report our clinical experience with rituximab in the treatment of 2 patients with idiopathic cutaneous angiitis who relapsed after treatment with high-dose corticosteroids and cyclophosphamide. A 39-year-old woman and a 51-year-old man presented with ulcerating maculopapular rash in both lower limbs which relapsed 6 months after treatment with a combination of high-dose corticosteroids and cyclophosphamide. After treatment with 2 g of rituximab, the first patient has still been in clinical remission for 32 months while the second has finished 28 months. Interestingly, CD19 which had dropped to <0.1 one week following the start of retuximab had increased to >0.5% 8 months later in both patients. Despite that, our patients are still in clinical remission. No significant side effects were noted during infusions and up to the period of follow-up. In conclusion, rituximab is a useful and safe agent in the treatment of idiopathic cutaneous angiitis refractory to conventional therapy. Clinical remission persists years after improvement of B-cell suppression.

The immunosuppressed traveler

This article reviews the normal immune response to vaccines. It describes the effect of different immunosuppressive therapies (glucocorticoids, inhibitors of calcineurin and mTOR, azathioprine, mycophenolate acid, methotrexate, depleting and nondepleting monoclonal antibodies, and tumor necrosis factor antagonists) on critical steps in the cellular and humoral immune responses to vaccines. The impact of age-related involution of thymus and bone marrow on the immune reconstitution in allogeneic hematopoietic cell transplant recipients and human immunodeficiency virus is covered. A practical approach to vaccinating and preparing travelers with severe immunosuppression is proposed.

Immunological aspects in chronic lymphocytic leukemia (CLL) development

Chronic lymphocytic leukemia (CLL) is unique among B cell malignancies in that the malignant clones can be featured either somatically mutated or unmutated IGVH genes. CLL cells that express unmutated immunoglobulin variable domains likely underwent final development prior to their entry into the germinal center, whereas those that express mutated variable domains likely transited through the germinal center and then underwent final development. Regardless, the cellular origin of CLL remains unknown. The aim of this review is to summarize immunological aspects involved in this process and to provide insights about the complex biology and pathogenesis of this disease. We propose a mechanistic hypothesis to explain the origin of B-CLL clones into our current picture of normal B cell development. In particular, we suggest that unmutated CLL arises from normal B cells with self-reactivity for apoptotic bodies that have undergone receptor editing, CD5 expression, and anergic processes in the bone marrow. Similarly, mutated CLL would arise from cells that, while acquiring self-reactivity for autoantigens-including apoptotic bodies-in germinal centers, are also still subject to tolerization mechanisms, including receptor editing and anergy. We believe that CLL is a proliferation of B lymphocytes selected during clonal expansion through multiple encounters with (auto)antigens, despite the fact that they differ in their state of activation and maturation. Autoantigens and microbial pathogens activate BCR signaling and promote tolerogenic mechanisms such as receptor editing/revision, anergy, CD5+ expression, and somatic hypermutation in CLL B cells. The result of these tolerogenic mechanisms is the survival of CLL B cell clones with similar surface markers and homogeneous gene expression signatures. We suggest that both immunophenotypic surface markers and homogenous gene expression might represent the evidence of several attempts to re-educate self-reactive B cells.

IgM memory B cells: a mouse/human paradox

Humoral memory is maintained by two types of persistent cells, memory B cells and plasma cells, which have different phenotypes and functions. Long-lived plasma cells can survive for a lifespan within a complex niche in the bone marrow and provide continuous protective serum antibody levels. Memory B cells reside in secondary lymphoid organs, where they can be rapidly mobilized upon a new antigenic encounter. Surface IgG has long been taken as a surrogate marker for memory in the mouse. Recently, however, we have brought evidence for a long-lived IgM memory B cell population in the mouse, while we have also argued that, in humans, these same cells are not classical memory B cells but marginal zone (MZ) B cells which, as opposed to their mouse MZ counterpart, recirculate and carry a mutated B cell receptor. In this review, we will discuss these apparently paradoxical results.

Rituximab therapy leads to reduced imprints of receptor revision in immunoglobulin κ and λ light chains

OBJECTIVE

Transient B cell depletion by rituximab (RTX) has become a specific treatment of rheumatoid arthritis (RA). Although phenotypic repopulation kinetics of B cell subsets are well documented, precise molecular analyses of the reconstituting immunoglobulin (Ig) genes encoding the B cell receptor in RA are sparse.

METHODS

A total of 708 individual CD19+CD27+ (memory) and CD19+CD27- (naive) B cells from 2 patients with RA were analyzed at baseline and 7 months after RTX at B cell repopulation. Ig light chain variable kappa (Vκ) and lambda (Vλ) light chain gene rearrangements were amplified, sequenced, and analyzed with a focus on receptor revision.

RESULTS

The naive as well as the memory repertoire repopulated polyclonally with diverse use of variable light chain gene families and minigenes. During the reconstitution phase, B cells used significantly fewer Jκ distal Vκ genes (p = 0.0006), with a higher frequency of somatic hypermutation of rearrangements employing Jκ5 compared to baseline in memory B cells. The use of Vλ rearrangements in regenerating B cells was also biased toward use of Vλ genes of the proximal cassette. In general, reemerging CD27+ Ig light chain genes were substantially more highly mutated than before RTX therapy (p < 0.0001, baseline vs during reconstitution).

CONCLUSION

Our data indicate that RTX therapy leads to generation of distinct Vκ/Jκ and Vλ/Jλ gene repertoires consistent with replenishment of antigen-experienced B cells by germinal centers. At baseline, the imprints of receptor revision appeared to be more striking, which indicates that receptor revision is active in patients with RA and can be reduced by RTX.

Immunological risk factors for infection after immunosuppressive and biologic therapies

Immunosuppressive and biologic therapies are costly and can involve a considerable risk of infection. Noninvasive diagnostic tools for early prediction of infection before and after administration of these therapies are of major interest. Serial longitudinal immune monitoring would provide data on immunocompetence and complement clinical follow-up protocols. Biomarkers of immune response may be useful to identify patients at risk of developing infection and who could be candidates for immunosuppressant dose reduction. This article focuses on the potential use of biomarkers of immune response to predict development of infection after immunosuppressive and biologic therapies in selected settings of autoimmune disease (rituximab for treatment of rheumatoid arthritis) and solid organ transplantation.

B-cell subsets in the joint compartments of seropositive and seronegative rheumatoid arthritis (RA) and No-RA arthritides express memory markers and ZAP70 and characterize the aggregate pattern irrespectively of the autoantibody status

The aim of the present study was to determine whether different subsets of B cells characterize synovial fluid (SF) or synovial tissue (ST) of seropositive or seronegative rheumatoid arthritis (RA) with respect to the peripheral blood (PB). PB, SF and ST of 14 autoantibody (AB)-positive (rheumatoid factor [RF]-IgM, RF-IgA, anti-citrullinated peptide [CCP]), 13 negative RA and 13 no-RA chronic arthritides were examined for B-cell subsets (Bm1-Bm5 and IgD-CD27 classifications), zeta-associated protein kinase-70 (ZAP70) expression on B cells and cytokine levels (interleukin [IL]-1β, tumor necrosis factor [TNF]-α, IL-6, IL-8 and monocyte chemotactic protein [MCP]-1). Synovial tissues were classified as aggregate and diffuse patterns. No differences were found in B-cell percentages or in subsets in PB and SF between AB(+) and AB(-) RA and no-RA. In both AB(+) and AB(-) RA (and no-RA), the percentage of CD19(+)/ZAP70(+) was higher in SF than in PB (AB(+): P = 0.03; AB(-): P = 0.01; no-RA: P = 0.01). Moreover, SF of both AB(+) and AB(-) RA (and no-RA) patients was characterized by a higher percentage of IgD-CD27(+) and IgD-CD27(-) B cells and lower percentage of IgD(+)CD27(-) (P < 0.05) B cells compared to PB. In SF, ZAP70 positivity is more represented in B cell CD27(+)/IgD(-)/CD38(-). The aggregate synovitis pattern was characterized by higher percentages of Bm5 cells in SF compared with the diffuse pattern (P = 0.05). These data suggest that no difference exists between AB(+) and AB(-) in B-cell subset compartmentalization. CD27(+)/IgD(-)/ZAP70(+) memory B cells accumulate preferentially in the joints of RA, suggesting a dynamic maturation of the B cells in this compartment.

B cells in the pathogenesis and treatment of rheumatoid arthritis

PURPOSE OF REVIEW

Our understanding of the multiple physiological and pathogenic functions of B cells in rheumatoid arthritis (RA) continues to expand. In turn, the availability of effective agents targeting the B cell compartment increases. In this review, we discuss novel insights into the roles of B cells in RA and recent evidence regarding the efficacy of B cell depletion and biomarkers of treatment response.

RECENT FINDINGS

Recent data have further elucidated the requirements for the generation of ectopic lymphoid structures in the rheumatoid synovium, their frequency, and role in pathogenesis. Additional studies have described the phenotype of infiltrating B cells in the synovium and the unexpected role for B cells in bone homeostasis. In addition to pathogenic roles for B cells, there is also mounting evidence for regulatory B cell subsets that may play a protective role. New data on radiographic progression, efficacy in early disease, the role of retreatment, and biomarkers of treatment response continue to refine the role of B cell depletion in the treatment armamentarium.

SUMMARY

The past few years have seen new advances in immunology applied to the study of RA with surprising observations and interesting new insights into cause and pathogenesis.