B cells and immunological tolerance

Cell and biomaterial delivery strategies to induce immune tolerance

The prevalence of immune-mediated disorders, including autoimmune conditions and allergies, is steadily increasing. However, current therapeutic approaches are often non-specific and do not address the underlying pathogenic condition, often resulting in impaired immunity and a state of generalized immunosuppression. The emergence of technologies capable of selectively inhibiting aberrant immune activation in a targeted, antigen (Ag)-specific manner by exploiting the body's intrinsic tolerance pathways, all without inducing adverse side effects, holds significant promise to enhance patient outcomes. In this review, we will describe the body's natural mechanisms of central and peripheral tolerance as well as innovative delivery strategies using cells and biomaterials targeting innate and adaptive immune cells to promote Ag-specific immune tolerance. Additionally, we will discuss the challenges and future opportunities that warrant consideration as we navigate the path toward clinical implementation of tolerogenic strategies to treat immune-mediated diseases.

Biological treatment for bullous pemphigoid

Background

Bullous pemphigoid (BP) is the most common autoimmune subepidermal bullous disease. Topical or systemic corticosteroids are often used as the first-line treatment. However, long-term corticosteroid use may lead to significant side effects. Therefore, various adjuvant immunosuppressant therapies are used as steroid-sparing agents, with accumulating reports of biological treatments for severely recalcitrant BP.

Objective

To describe the clinical and immunological features of a series of patients with recalcitrant BP treated with immunobiological therapies. To assess the efficacy and safety of their therapies.

Methods

Patients receiving biological treatment for BP from two centers were assessed. Here, we described the clinical, immunopathological, and immunofluorescence findings of adult patients with BP and analyzed the clinical response and adverse events associated with various biological therapies.

Results

We identified nine eligible patients treated with rituximab (seven), omalizumab (three), or dupilumab (one). The mean age at diagnosis was 60.4 years, the average BP duration before biologic initiation was 1.9 years, and the average previous treatment failure was 2.11 therapies. The mean follow-up period from the first biological treatment to the last visit was 29.3 months. Satisfactory response, defined as clinical improvement, was achieved in 78% (7) of the patients, and total BP clearance was achieved in 55% (5) of the patients at the last follow-up visit. Additional rituximab courses improved the disease outcomes. No adverse events were reported.

Conclusions

Efficient and safe novel therapies can be considered in recalcitrant steroid-dependent BP non-responsive to conventional immunosuppressant therapies.

Rituximab, Omalizumab, and Dupilumab Treatment Outcomes in Bullous Pemphigoid: A Systematic Review

Background

Bullous pemphigoid (BP) is the most common autoimmune subepidermal bullous disease of the skin. First-line treatment of systemic corticosteroids may cause serious adverse events. Rituximab, omalizumab, and dupilumab should be explored as alternative treatment options to improve outcomes.

Objective

To systematically review the rituximab, omalizumab, and dupilumab treatment outcomes in bullous pemphigoid.

Methods

A PubMed, Embase, Web of Science, and Cochrane library search were conducted on March 10, 2022. A total of 75 studies were included using Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Results

Use of rituximab (n=122), omalizumab (n=53) and dupilumab (n=36) were reported in 211 patients with BP. Rituximab led to complete remission in 70.5% (n=86/122) and partial remission in 23.8% (n=29/122) of patients within 5.7 months, with a recurrence rate of 20.5% (n=25/122). 9.0% (n=11/122) of patients died and infection (6.6%, n=8/122) was the most common adverse event. Omalizumab led to complete remission in 67.9% (n=36/53) and partial remission in 20.8% (n=11/53) of patients within 6.6 months, with a recurrence rate of 5.7% (n=3/53). 1.9% (n=1/53) of patients died and thrombocytopenia (1.9%, n=1/53) was observed as the most common adverse event. Dupilumab led to complete remission in 66.7% (n=24/36) and partial remission in 19.4% (n=7/36) of patients within 4.5 months of treatment without any reported adverse events, with a recurrence rate of 5.6% (n=2/36).

Conclusions

Rituximab, omalizumab, and dupilumab have similar clinical benefits for BP patients. However, rituximab resulted in higher recurrence rates, adverse events, and mortality rates.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022316454.

High-Throughput Detection of Autoantigen-Specific B Cells Among Distinct Functional Subsets in Autoimmune Donors

Antigen-specific B cells (ASBCs) can drive autoimmune disease by presenting autoantigen to cognate T cells to drive their activation, proliferation, and effector cell differentiation and/or by differentiating into autoantibody-secreting cells. Autoantibodies are frequently used to predict risk and diagnose several autoimmune diseases. ASBCs can drive type 1 diabetes even when immune tolerance mechanisms block their differentiation into antibody-secreting cells. Furthermore, anti-histidyl tRNA synthetase syndrome patients have expanded IgM⁺ Jo-1-binding B cells, which clinically diagnostic IgG Jo-1 autoantibodies may not fully reflect. Given the potential disconnect between the pathologic function of ASBCs and autoantibody secretion, direct study of ASBCs is a necessary step towards developing better therapies for autoimmune diseases, which often have no available cure. We therefore developed a high-throughput screening pipeline to 1) phenotypically identify specific B cell subsets, 2) expand them in vitro, 3) drive them to secrete BCRs as antibody, and 4) identify wells enriched for ASBCs through ELISA detection of antibody. We tested the capacity of several B cell subset(s) to differentiate into antibody-secreting cells following this robust stimulation. IgM⁺ and/or IgD⁺, CD27^- memory, memory, switched memory, and B_ND B cells secreted B cell receptor (BCR) as antibody following in vitro stimulation, whereas few plasmablasts responded. Bimodal responses were observed across autoimmune donors for IgM⁺ CD21^lo and IgM^- CD21^lo B cells, consistent with documented heterogeneity within the CD21^lo subset. Using this approach, we detected insulin-binding B cell bias towards CD27^- memory and CD27⁺ memory subsets in pre-symptomatic type 1 diabetes donors. We took advantage of routine detection of Jo-1-binding B cells in Jo-1+ anti-histidyl tRNA synthetase syndrome patients to show that Jo-1-binding B cells and total B cells expanded 20-30-fold using this culture system. Overall, these studies highlight technology that is amenable to small numbers of cryopreserved peripheral blood mononuclear cells that enables interrogation of phenotypic and repertoire attributes of ASBCs derived from autoimmune patients.

B Cell Aberrance in Lupus: the Ringleader and the Solution

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease with high heterogeneity but the common characterization of numerous autoantibodies and systemic inflammation which lead to the damage of multiple organs. Aberrance of B cells plays a pivotal role in the immunopathogenesis of SLE via both antibody-dependent and antibody-independent manners. Escape of autoreactive B cells from the central and peripheral tolerance checkpoints, over-activation of B cells and their excessive cytokines release which drive T cells and dendritic cells stimulation, and dysregulated surface molecules, as well as intracellular signal pathways involved in B cell biology, are all contributing to B cell aberrance and participating in the pathogenesis of SLE. Based on that rationale, targeting aberrance of B cells and relevant molecules and pathways is expected to be a promising strategy for lupus control. Multiple approaches targeting B cells through different mechanisms have been attempted, including B-cell depletion via monoclonal antibodies against B-cell-specific molecules, blockade of B-cell survival and activation factors, suppressing T-B crosstalk by interrupting costimulatory molecules and inhibiting intracellular activation signaling cascade by targeting pathway molecules in B cells. Though most attempts ended in failure, the efficacy of B-cell targeting has been encouraged by the FDA approval of belimumab that blocks B cell-activating factor (BAFF) and the recommended use of anti-CD20 as a remedial therapy in refractory lupus. Still, quantities of clinical trials targeting B cells or relevant molecules are ongoing and some of them have displayed promising preliminary results. Additionally, advances in multi-omics studies help deepen our understandings of B cell biology in lupus and may promote the discovery of novel potential therapeutic targets. The combination of real-world data with basic research achievements may pave the road to conquering lupus.

A Prospective Study on Long-Term Clinical Outcomes of Patients With Lupus Nephritis Treated With an Intensified B-Cell Depletion Protocol Without Maintenance Therapy

Background

We aimed to investigate the safety and efficacy of an intensified B-cell depletion induction therapy (IBCDT) without immunosuppressive maintenance regimen compared with standard of care in biopsy-proven lupus nephritis (LN).

Methods

Thirty patients were administered an IBCDT (4 weekly rituximab [RTX] 375 mg/m² and 2 more doses after 1 and 2 months; 2 infusions of 10 mg/kg cyclophosphamide [CYC], 3 methylprednisolone pulses), followed by oral prednisone (tapered to 5 mg/d by the third month). No immunosuppressive maintenance therapy was given. Thirty patients matched for LN class and age were selected as controls: 20 received 3 methylprednisolone pulses days followed by oral prednisone and mycophenolate mofetil (MMF) 2 to 3 g/d, whereas 10 were given the Euro Lupus CYC. MMF (1-2 g/daily) or azathioprine (AZA, 1-2 mg/kg/day) were given for > 3 years as a maintenance therapy.

Results

At 12 months, complete renal remission was observed in 93% of patients on IBCDT, in 62.7% on MMF, and in 75% on CYC (P = 0.03); the dose of oral prednisone was lower in the IBCDT group (mean ± SD 2.9 ± 5.0 mg/dl) than MMF (10.5 ± 8.0 mg/d, P < 0.01) or CYC group (7.5 ± 9.0 mg/d, P < 0.01). Mean follow-up after treatment was 44.5 months (interquartile range [IQR] 36-120 months), 48.6 months (IQR 36-120 months), and 45.3 (IQR 36-120 months) for IBCDT, MMF, and CYC, respectively. At their last follow-up visit, we observed no significant differences in proteinuria and serum creatinine, nor in the frequency of new flares among the 3 groups.

Conclusion

In biopsy-proven LN, the IBCDT without further immunosuppressive maintenance therapy was shown to be as effective as conventional regimen of MMF or CYC followed by >3-year maintenance either MMF or AZA regimen. Moreover, the use of IBCDT was associated with a marked reduction of glucocorticoid cumulative dose.

The advantage of Sirolimus in amplifying regulatory B cells and regulatory T cells in liver transplant patients

Sirolimus has been shown to ameliorate steroid-resistant rejection and induce long-term immune tolerance among liver transplant patients. However, the detailed mechanism of how Sirolimus achieve these advantages is still lacking. This study attempts to reveal some possible mechanisms by investigating regulatory B cells (Bregs), regulatory T cells (Tregs) and some cytokines in liver transplant recipients whose Tacrolimus was partially converted to Sirolimus. The results showed that CD19⁺CD24⁺CD38⁺Bregs and CD4⁺CD25⁺FoxP3⁺Tregs increased significantly during the first month after drug conversion (P < 0.01 and P < 0.05). The percentages of IL-10⁺Bregs and TGF-β₁⁺Bregs were also elevated (P < 0.05 and P < 0.01), and the same trend was observed in the levels of IL-10 and TGF-β₁ (P < 0.01 and P < 0.01). However, in the observation period, these investigated lymphocyte subsets and cytokines didn't change significantly in patients without Sirolimus usage. The incidence of biliary stenosis in the conversion group were significantly lower than that in the control group (P < 0.05). At the same time, in vitro experiments showed that Sirolimus could significantly amplify Bregs and Tregs (P < 0.01 and P < 0.01) while Tacrolimus did not show the amplifications effects. Sirolimus' function of amplifying Bregs was weakened, and its function of amplifying Tregs even disappeared after IL-10 and TGF-β₁ were neutralized. In conclusion, Sirolimus could amplify Bregs and Tregs among liver transplant recipient, which might be benefit to mitigate the immune response, decrease chances of rejection and alleviate biliary complication. IL-10 and TGF-β₁ may play important roles during this process.

[The role of laboratory biomarkers in monitoring of rituximab biosimilar therapy (Acellbia, "BIOCAD") in patients with rheumatoid arthritis]

AIM

to evaluate the role of laboratory biomarkers in monitoring effectiveness of rituximab (RTM) biosimilar therapy in a total dose of 1200 mg.

MATERIALS AND METHODS

20 patients (pts) with rheumatoid arthritis (RA) (18 woman, mean age 61.5(54-66.5) years, mean disease duration 39.5(20-84) months, mean DAS28 5.6(4.9-6.8)) received two intravenous RTM biosimilar infusions (600 mg №2) in combination with DMARDs and glucocorticoids. Laboratory biomarkers were assessed at baseline and weeks 12 and 24 after the first infusion of RTX.

RESULTS

RTM biosimilar induced decreases in DAS28, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) at week 12 and 24, p.

Understanding B-cell activation and autoantibody repertoire selection in systemic lupus erythematosus: A B-cell immunomics approach

Understanding antibody repertoires and in particular, the properties and fates of B cells expressing potentially pathogenic antibodies is critical to define the mechanisms underlying multiple immunological diseases including autoimmune and allergic conditions as well as transplant rejection. Moreover, an integrated knowledge of the antibody repertoires expressed by B cells and plasma cells (PC) of different functional properties and longevity is essential to develop new therapeutic strategies, better biomarkers for disease segmentation, and new assays to measure restoration of B-cell tolerance or, at least, of normal B-cell homeostasis. Reaching these goals, however, will require a more precise phenotypic, functional and molecular definition of B-cell and PC populations, and a comprehensive analysis of the antigenic reactivity of the antibodies they express. While traditionally hampered by technical and ethical limitations in human experimentation, new technological advances currently enable investigators to address these questions in a comprehensive fashion. In this review, we shall discuss these concepts as they apply to the study of Systemic Lupus Erythematosus.

Polymeric micro- and nanoparticles for immune modulation

New advances in biomaterial-based approaches to modulate the immune system are being applied to treat cancer, infectious diseases, and autoimmunity. Particulate systems are especially well-suited to deliver immunomodulatory factors to immune cells since their small size allows them to engage cell surface receptors or deliver cargo intracellularly after internalization. Biodegradable polymeric particles are a particularly versatile platform for the delivery of signals to the immune system because they can be easily surface-modified to target specific receptors and engineered to release encapsulated cargo in a precise, sustained manner. Micro- and nanoscale systems have been used to deliver a variety of therapeutic agents including monoclonal antibodies, peptides, and small molecule drugs that function to activate the immune system against cancer or infectious disease, or suppress the immune system to combat autoimmune diseases and transplant rejection. This review provides an overview of recent advances in the development of polymeric micro- and nanoparticulate systems for the presentation and delivery of immunomodulatory agents targeted to a variety of immune cell types including APCs, T cells, B cells, and NK cells.

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 cells in multiple sclerosis therapy-A comprehensive review

For decades, B cells were ignored in multiple sclerosis (MS) pathogenesis, and the disease was always regarded as a T cell-mediated disorder. Recent evidence shows that there is an antigen-driven B-cell response in the central nervous system of patients with MS, and memory B cells/plasma cells are detectable in MS lesions. The striking efficacy of B cell-depleting therapies in reducing the inflammatory activity of the disease highlights that B cells may play more pathogenetic roles than expected. B cells express several unique characteristic markers on their surface, for example, CD19, CD20 molecules, that provide selective targets for monoclonal antibodies. In this respect, several B cell-targeted therapies emerged, including anti-CD20 antibodies (rituximab, ocrelizumab, and ofatumumab), anti-CD19 antibody (inebilizumab), and agents targeting the BAFF/APRIL signaling pathway (atacicept, belimumab, and LY2127399). In this review, we discuss, in detail, the immunobiology of B cells and their protective and destructive roles in MS pathogenesis. In the second part, we list the completed and ongoing clinical trials investigating the safety and efficacy of B cell-related monoclonal antibodies in MS.

Antinuclear antibodies in autoimmune and allergic diseases

Antinuclear antibodies (ANA) are primarily significant in the diagnosis of systemic connective tissue diseases. The relationship between their occurrence in allergic diseases is poorly documented. However, the mechanism of allergic and autoimmune diseases has a common thread. In both cases, an increased production of IgE antibodies and presence of ANA in selected disease entities is observed. Equally important is the activation of basophils secreting proinflammatory factors and affecting the differentiation of TH17 lymphocytes. Both autoimmune and allergic diseases have complex multi-pathogenesis and often occur in genetically predisposed individuals. The presence of antinuclear antibodies was confirmed in many systemic connective tissue diseases and some allergic diseases. Examples include atopic dermatitis, non-allergic asthma, and pollen allergy. Co-occurring allergic and autoimmune disorders induce further search for mechanisms involved in the aetiopathogenesis of both groups of diseases.

Chronic Exposure to Malaria Is Associated with Inhibitory and Activation Markers on Atypical Memory B Cells and Marginal Zone-Like B Cells

In persistent infections that are accompanied by chronic immune activation, such as human immunodeficiency virus, hepatitis C virus, and malaria, there is an increased frequency of a phenotypically distinct subset of memory B cells lacking the classic memory marker CD27 and showing a reduced capacity to produce antibodies. However, critical knowledge gaps remain on specific B cell changes and immune adaptation in chronic infections. We hypothesized that expansion of atypical memory B cells (aMBCs) and reduction of activated peripheral marginal zone (MZ)-like B cells in constantly exposed individuals might be accompanied by phenotypic changes that would confer a tolerogenic profile, helping to establish tolerance to infections. To better understand malaria-associated phenotypic abnormalities on B cells, we analyzed peripheral blood mononuclear cells from 55 pregnant women living in a malaria-endemic area of Papua Nueva Guinea and 9 Spanish malaria-naïve individuals using four 11-color flow cytometry panels. We assessed the expression of markers of B cell specificity (IgG and IgM), activation (CD40, CD80, CD86, b220, TACI, and CD150), inhibition (PD1, CD95, and CD71), and migration (CCR3, CXCR3, and CD62l). We found higher frequencies of active and resting aMBC and marked reduction of MZ-like B cells, although changes in absolute cell counts could not be assessed. Highly exposed women had higher PD1+-, CD95+-, CD40+-, CD71+-, and CD80+-activated aMBC frequencies than non-exposed subjects. Malaria exposure increased frequencies of b220 and proapoptotic markers PD1 and CD95, and decreased expression of the activation marker TACI on MZ-like B cells. The increased frequencies of inhibitory and apoptotic markers on activated aMBCs and MZ-like B cells in malaria-exposed adults suggest an immune-homeostatic mechanism for maintaining B cell development and function while simultaneously downregulating hyperreactive B cells. This mechanism would keep the B cell activation threshold high enough to control infection but impaired enough to tolerate it, preventing systemic inflammation.

Sequential monitoring of lymphocyte subsets and of T-and-B cell neogenesis indexes to identify time-varying immunologic profiles in relation to graft-versus-host disease and relapse after allogeneic stem cell transplantation

T and B lymphocyte subsets have been not univocally associated to Graft-versus-host disease (GVHD) and relapse of hematological malignancies after stem cell transplantation (SCT). Their sequential assessment together with B and T cell neogenesis indexes has been not thoroughly analysed in relation to these changing and interrelated immunologic/clinic events yet.

Lymphocyte subsets in peripheral blood (PB) and B and T cell neogenesis indexes were analysed together at different time points in a prospective study of 50 patients. Principal component analysis (PCA) was used as first step of multivariate analysis to address issues related to a high number of variables versus a relatively low number of patients. Multivariate analysis was completed by Fine-Gray proportional hazard regression model. PCA identified 3 clusters of variables (PC1-3), which correlated with acute GVHD: PC1 (pre-SCT: KRECs≥6608/ml, unswitched memory B <2.4%, CD4+T_CM cells <45%; HR 0.5, p = 0.001); PC2 (at aGVHD onset: CD4+>44%, CD8+T_CM cells>4%; HR 1.9, p = 0.01), and PC3 (at aGVHD onset: CD4+TEM_RA<1, total Treg<4, Treg_EM <2 cells/μl; HR 0.5, p = 0.002). Chronic GVHD was associated with one PC (Treg_EM <2 cells/μl at day+28, CD8+TEM_RA<43% at day+90, immature B cells<6 cells/μl and KRECs<11710/ml at day+180; HR 0.4, P = 0.001). Two PC correlated with relapse: PC1 (pre-SCT: CD4+ <269, CD4+T_CM <120, total Treg <18, Treg_CM <8 cells/μl; HR 4.0, p = 0.02); PC2 (pre-SCT mature CD19+ >69%, switched memory CD19+ = 0 cells and KRECs<6614/ml at +90; HR 0.1, p = 0.008). All these immunologic parameters were independent indicators of chronic GVHD and relapse, also considering the possible effect of previous steroid-therapy for acute GVHD. Specific time-varying immunologic profiles were associated to GVHD and relapse. Pre-SCT host immune-microenvironment and changes of B cell homeostasis could influence GVH- and Graft-versus-Tumor reactions. The paradoxical increase of EM Treg in PB of patients with GVHD could be explained by their compartmentalization outside lymphoid tissues, which are of critical relevance for regulation of GVH reactions.

Encapsulating an Immunosuppressant Enhances Tolerance Induction by Siglec-Engaging Tolerogenic Liposomes

Unwanted antibody responses significantly impact human health, and current options for treating deleterious antibody responses largely rely on broad immunosuppressants that can compromise overall immunity. A desirable alternative is to induce antigen-specific immune tolerance. We have shown that co-presentation of antigen and ligands of B cell sialic acid-binding immunoglobulin-like lectins (Siglecs) on a liposomal nanoparticle induces antigen-specific tolerance. Although Siglec-engaging tolerance-inducing antigenic liposomes (STALs) induce robust B cell tolerance in naïve mice, the full potential of STALs requires long-term tolerance induction and suppression of an ongoing immune response. We hypothesized that STALs encapsulated with rapamycin (RAPA), an immunomodulator, could improve the efficacy of STALs and potentially enable their use in the context of immunological memory. Here, we showed that formulation of STALs with RAPA produced enhanced tolerance induction in naïve mice compared to STALs without RAPA but had minimal impact on inducing tolerance in previously sensitized mice. These findings indicate that the addition of immunomodulators to STALs could be beneficial in tolerance induction and support future development of STALs for the treatment of allergy and autoimmune diseases.

Individualized Immunosuppressive Protocol of Liver Transplant Recipient Should be Made Based on Splenic Function Status

BACKGROUND

Lymphocyte subsets play important roles in rejection in liver transplant recipients, and the effect of splenic function on these roles remains unknown. The aim of this study was to explore the feasibility to adjust immunosuppressive agents based on splenic function status through detecting the lymphocyte subsets in liver transplantBeijing recipients.

METHODS

The lymphocyte subsets of 49 liver transplant recipients were assessed in the 309th Hospital of Chinese People's Liberation Army between June 2014 and August 2015. The patients were divided into splenectomy group (n = 9), normal splenic function group (n = 24), and hypersplenism group (n = 16). The percentages and counts of CD4+ T, CD8+ T, natural killer (NK) cell, B-cell, regulatory B-cell (Breg), and regulatory T-cell (Treg) were detected by flow cytometer. In addition, the immunosuppressive agents, histories of rejection and infection, and postoperative time of the patients were compared among the three groups.

RESULTS

There was no significant difference of clinical characteristics among the three groups. The percentage of CD19+CD24+CD38+ Breg was significantly higher in hypersplenism group than normal splenic function group and splenectomy group (3.29 ± 0.97% vs. 2.12 ± 1.08% and 1.90 ± 0.99%, P = 0.001). The same result was found in CD4+CD25+FoxP3+ Treg percentage (0.97 ± 0.39% vs. 0.54 ± 0.31% and 0.56 ± 0.28%, P = 0.001). The counts of CD8+ T-cell, CD4+ T-cell, and NK cell were significantly lower in hypersplenism group than normal splenic function group (254.25 ± 149.08 vs. 476.96 ± 225.52, P= 0.002; 301.69 ± 154.39 vs. 532.50 ± 194.42, P= 0.000; and 88.56 ± 63.15 vs. 188.33 ± 134.51, P = 0.048). Moreover, the counts of CD4+ T-cell and NK cell were significantly lower in hypersplenism group than splenectomy group (301.69 ± 154.39 vs. 491.89 ± 132.31, P= 0.033; and 88.56 ± 63.15 vs. 226.00 ± 168.85, P = 0.032).

CONCLUSION

Splenic function status might affect the immunity of liver transplant recipients, that should be considered when we make immunosuppressive protocols.

B-cell subsets, signaling and their roles in secretion of autoantibodies

B cells play a pivotal role in the pathogenesis of autoimmune diseases. In patients with systemic lupus erythematosus (SLE), the percentages of plasmablasts and IgD−CD27− double-negative memory B cells in peripheral blood are significantly increased, while IgD+CD27+ IgM memory B cells are significantly decreased compared to healthy donors. The phenotypic change is significantly associated with disease activity and concentration of autoantibodies. Treatment of B-cell depletion using rituximab results in the reconstitution of peripheral B cells in SLE patients with subsequent improvement in disease activity. Numerous studies have described abnormalities in B-cell receptor (BCR)-mediated signaling in B cells of SLE patients. Since differences in BCR signaling are considered to dictate the survival or death of naïve and memory B cells, aberrant BCR signal can lead to abnormality of B-cell subsets in SLE patients. Although Syk and Btk function as key molecules in BCR signaling, their pathological role in SLE remains unclear. We found that Syk and Btk do not only transduce activation signal through BCR, but also mediate crosstalk between BCR and Toll-like receptor (TLR) as well as BCR and JAK-STAT pathways in human B cells in vitro. In addition, pronounced Syk and Btk phosphorylation was observed in B cells of patients with active SLE compared to those of healthy individuals. The results suggest the involvement of Syk and Btk activation in abnormalities of BCR-mediated signaling and B-cell phenotypes during the pathological process of SLE and that Syk, Btk and JAK are potential therapeutic targets in SLE.

Evolution of the Humoral Response during HCV Infection: Theories on the Origin of Broadly Neutralizing Antibodies and Implications for Vaccine Design

Similar to human immunodeficiency virus (HIV)-1, vaccine-induced elicitation of broadly neutralizing (bNt) antibodies (Abs) is gaining traction as a key goal toward the eradication of the hepatitis C virus (HCV) pandemic. Previously, the significance of the Ab response against HCV was underappreciated given the prevailing evidence advancing the role of the cellular immune response in clearance and overall control of the infection. However, recent findings have driven growing interest in the humoral arm of the immune response and in particular the role of bNt responses due to their ability to confer protective immunity upon passive transfer in animal models. Nevertheless, the origin and development of bNt Abs is poorly understood and their occurrence is rare as well as delayed with emergence only observed in the chronic phase of infection. In this review, we characterize the interplay between the host immune response and HCV as it progresses from the acute to chronic phase of infection. In addition, we place these events in the context of current hypotheses on the origin of bNt Abs against the HIV-1, whose humoral immune response is better characterized. Based on the increasing significance of the humoral immune response against HCV, characterization of these events may be critical in understanding the development of the bNt responses and, thus, provide strategies toward effective vaccine design.

Polychromatic flow cytometry in evaluating rheumatic disease patients

B cells are central players in multiple autoimmune rheumatic diseases as a result of the imbalance between pathogenic and protective B-cell functions, which are presumably mediated by distinct populations. Yet the functional role of different B-cell populations and the contribution of specific subsets to disease pathogenesis remain to be fully understood owing to a large extent to the use of pauci-color flow cytometry. Despite its limitations, this approach has been instrumental in providing a global picture of multiple B-cell abnormalities in multiple human rheumatic diseases, more prominently systemic lupus erythematosus, rheumatoid arthritis and Sjogren’s syndrome. Accordingly, these studies represent the focus of this review. In addition, we also discuss the added value of tapping into the potential of polychromatic flow cytometry to unravel a higher level of B-cell heterogeneity, provide a more nuanced view of B-cell abnormalities in disease and create the foundation for a precise understanding of functional division of labor among the different phenotypic subsets. State-of-the-art polychromatic flow cytometry and novel multidimensional analytical approaches hold tremendous promise for our understanding of disease pathogenesis, the generation of disease biomarkers, patient stratification and personalized therapeutic approaches.

Primary Sjögren's syndrome is characterized by distinct phenotypic and transcriptional profiles of IgD+ unswitched memory B cells

OBJECTIVE

The significance of distinct B cell abnormalities in primary Sjögren's syndrome (SS) remains to be established. We undertook this study to analyze the phenotype and messenger RNA (mRNA) transcript profiles of B cell subsets in patients with primary SS and to compare them with those in sicca syndrome patients and healthy controls.

METHODS

CD19+ B cells from 26 patients with primary SS, 27 sicca syndrome patients, and 22 healthy controls were analyzed by flow cytometry. Gene expression profiles of purified B cell subsets (from 3-5 subjects per group per test) were analyzed using Affymetrix gene arrays.

RESULTS

Patients with primary SS had lower frequencies of CD27+IgD- switched memory B cells and CD27+IgD+ unswitched memory B cells compared with healthy controls. Unswitched memory B cell frequencies were also lower in sicca syndrome patients and correlated inversely with serologic hyperactivity in both disease states. Further, unswitched memory B cells in primary SS had lower expression of CD1c and CD21. Gene expression analysis of CD27+ memory B cells separated patients with primary SS from healthy controls and identified a subgroup of sicca syndrome patients with a primary SS-like transcript profile. Moreover, unswitched memory B cell gene expression analysis identified 187 genes differentially expressed between patients with primary SS and healthy controls.

CONCLUSION

A decrease in unswitched memory B cells with serologic hyperactivity is characteristic of both established primary SS and a subgroup of sicca syndrome, which suggests the value of these B cells both as biomarkers of future disease progression and for understanding disease pathogenesis. Overall, the mRNA transcript analysis of unswitched memory B cells suggests that their activation in primary SS takes place through innate immune pathways in the context of attenuated antigen-mediated adaptive signaling. Thus, our findings provide important insight into the mechanisms and potential consequences of decreased unswitched memory B cells in primary SS.

Pathogenesis and potential therapeutic targets in systemic lupus erythematosus: from bench to bedside

Systemic lupus erythematosus (SLE) is considered an autoimmune disease with multiorgan involvement. Many advances have been made during the last decade regarding inflammatory pathways, genetic and epigenetic alterations, adaptive and innate immune system mechanisms specifically involved in SLE pathogenesis. Apoptosis has been proposed as an important player in SLE pathogenesis more than a decade ago. However, only recently new key apoptotic pathways have been investigated and the link between apoptotic debris containing autoantigens, innate immunity and ongoing inflammation has been further elucidated. Better understanding of cellular mechanisms and involved cytokines contributed to the development of new biological drugs specifically addressed for SLE therapy.

Rationale for B cell targeting in SLE

B cells are central pathogenic players in systemic lupus erythematosus and multiple other autoimmune diseases through antibody production as well as antibody independent function. At the same time, B cells are known to play important regulatory functions that may protect against autoimmune manifestations. Yet, the functional role of different B cell populations and their contribution to disease remain to be understood. The advent of agents that specifically target B cells, in particular anti-CD20 and ant-BLyS antibodies, have demonstrated the efficacy of this approach for the treatment of human autoimmunity. The analysis of patients treated with these and other B cell agents provides a unique opportunity to understand the correlates of clinical response and the significance of different B cell subsets. Here, we discuss this information and how it could be used to better understand SLE and improve the rational design of B cell-directed therapies in this disease.

Differences in the composition of the human antibody repertoire by B cell subsets in the blood

The vast initial diversity of the antibody repertoire is generated centrally by means of a complex series of V(D)J gene rearrangement events, variation in the site of gene segment joining, and TdT catalyzed N-region addition. Although the diversity is great, close inspection has revealed distinct and unique characteristics in the antibody repertoires expressed by different B cell developmental subsets. In order to illustrate our approach to repertoire analysis, we present an in-depth comparison of V(D)J gene usage, hydrophobicity, length, D_H reading frame, and amino acid usage between heavy chain repertoires expressed by immature, transitional, mature, memory IgD⁺, memory IgD⁻, and plasmacytes isolated from the blood of a single individual. Our results support the view that in both human and mouse, the H chain repertoires expressed by individual, developmental B cell subsets appear to differ in sequence content. Sequencing of unsorted B cells from the blood is thus likely to yield an incomplete or compressed view of what is actually happening in the immune response of the individual. Our findings support the view that studies designed to correlate repertoire expression with diseases of immune function will likely require deep sequencing of B cells sorted by subset.

Involvement of suppressive B-lymphocytes in the mechanism of tolerogenic dendritic cell reversal of type 1 diabetes in NOD mice

The objective of the study was to identify immune cell populations, in addition to Foxp3+ T-regulatory cells, that participate in the mechanisms of action of tolerogenic dendritic cells shown to prevent and reverse type 1 diabetes in the Non-Obese Diabetic (NOD) mouse strain. Co-culture experiments using tolerogenic dendritic cells and B-cells from NOD as well as transgenic interleukin-10 promoter-reporter mice along with transfer of tolerogenic dendritic cells and CD19+ B-cells into NOD and transgenic mice, showed that these dendritic cells increased the frequency and numbers of interleukin-10-expressing B-cells in vitro and in vivo. The expansion of these cells was a consequence of both the proliferation of pre-existing interleukin-10-expressing B-lymphocytes and the conversion of CD19+ B-lymphcytes into interleukin-10-expressing cells. The tolerogenic dendritic cells did not affect the suppressive activity of these B-cells. Furthermore, we discovered that the suppressive murine B-lymphocytes expressed receptors for retinoic acid which is produced by the tolerogenic dendritic cells. These data assist in identifying the nature of the B-cell population increased in response to the tolerogenic dendritic cells in a clinical trial and also validate very recent findings demonstrating a mechanistic link between human tolerogenic dendritic cells and immunosuppressive regulatory B-cells.

Molecular basis of 9G4 B cell autoreactivity in human systemic lupus erythematosus

9G4(+) IgG Abs expand in systemic lupus erythematosus (SLE) in a disease-specific fashion and react with different lupus Ags including B cell Ags and apoptotic cells. Their shared use of VH4-34 represents a unique system to understand the molecular basis of lupus autoreactivity. In this study, a large panel of recombinant 9G4(+) mAbs from single naive and memory cells was generated and tested against B cells, apoptotic cells, and other Ags. Mutagenesis eliminated the framework-1 hydrophobic patch (HP) responsible for the 9G4 idiotype. The expression of the HP in unselected VH4-34 cells was assessed by deep sequencing. We found that 9G4 Abs recognize several Ags following two distinct structural patterns. B cell binding is dependent on the HP, whereas anti-nuclear Abs, apoptotic cells, and dsDNA binding are HP independent and correlate with positively charged H chain third CDR. The majority of mutated VH4-34 memory cells retain the HP, thereby suggesting selection by Ags that require this germline structure. Our findings show that the germline-encoded HP is compulsory for the anti-B cell reactivity largely associated with 9G4 Abs in SLE but is not required for reactivity against apoptotic cells, dsDNA, chromatin, anti-nuclear Abs, or cardiolipin. Given that the lupus memory compartment contains a majority of HP(+) VH4-34 cells but decreased B cell reactivity, additional HP-dependent Ags must participate in the selection of this compartment. This study represents the first analysis, to our knowledge, of VH-restricted autoreactive B cells specifically expanded in SLE and provides the foundation to understand the antigenic forces at play in this disease.

Metabolic alterations and increased liver mTOR expression precede the development of autoimmune disease in a murine model of lupus erythematosus

Although metabolic syndrome (MS) and systemic lupus erythematosus (SLE) are often associated, a common link has not been identified. Using the BWF1 mouse, which develops MS and SLE, we sought a molecular connection to explain the prevalence of these two diseases in the same individuals. We determined SLE- markers (plasma anti-ds-DNA antibodies, splenic regulatory T cells (Tregs) and cytokines, proteinuria and renal histology) and MS-markers (plasma glucose, non-esterified fatty acids, triglycerides, insulin and leptin, liver triglycerides, visceral adipose tissue, liver and adipose tissue expression of 86 insulin signaling-related genes) in 8-, 16-, 24-, and 36-week old BWF1 and control New-Zealand-White female mice. Up to week 16, BWF1 mice showed MS-markers (hyperleptinemia, hyperinsulinemia, fatty liver and visceral adipose tissue) that disappeared at week 36, when plasma anti-dsDNA antibodies, lupus nephritis and a pro-autoimmune cytokine profile were detected. BWF1 mice had hyperleptinemia and high splenic Tregs till week 16, thereby pointing to leptin resistance, as confirmed by the lack of increased liver P-Tyr-STAT-3. Hyperinsulinemia was associated with a down-regulation of insulin related-genes only in adipose tissue, whereas expression of liver mammalian target of rapamicyn (mTOR) was increased. Although leptin resistance presented early in BWF1 mice can slow-down the progression of autoimmunity, our results suggest that sustained insulin stimulation of organs, such as liver and probably kidneys, facilitates the over-expression and activity of mTOR and the development of SLE.

Cell type-specific eQTLs in the human immune system

A new study reports the mapping of gene expression in primary immune cell subsets, showing the presence of cell type-specific cis and trans expression quantitative trait loci (eQTLs). The identification of cell type-specific trans-regulated networks can inform functional studies of susceptibility loci identified from genome-wide association studies for human complex diseases.

Immunological approaches for tolerance induction in allergy

Allergy is the consequence of an inappropriate inflammatory immune response generated against harmless environmental antigens. In allergic disorders such as asthma and rhinitis, the Th2 mediated phenotype is a result of loss of peripheral tolerance mechanisms. In cases such as these, approaches such as immunotherapy attempt to treat the underlying cause of allergic disease by restoring tolerance. Immunotherapy initiates many complex mechanisms within the immune system that result in initiation of innate immunity, activation of both cellular and humoral B cell immunity, as well as triggering T regulatory subsets which are major players in the establishment of peripheral tolerance. Though studies clearly demonstrate immunotherapy to be efficacious, research to improve this treatment is ongoing. Investigation of allergenicity versus immunogenicity, native versus modified allergens, and the use of adjuvant and modality of dosing are all current strategies for immunotherapy advancement that will be reviewed in this article.

Selection of individual VH genes occurs at the pro-B to pre-B cell transition

B cells are subjected to selection at multiple checkpoints during their development. The selection of Ab H chains is difficult to study because of the large diversity of the CDR3. To study the selection of individual Ab H chain V region genes (V(H)), we performed CDR3 spectratyping of ∼ 75-300 rearrangements per individual V(H) in C57BL6/J mice. We measured the fraction of rearrangements that were in-frame in B cell DNA. We demonstrate that individual V(H)s have different fractions of in-frame rearrangements (IF fractions) ranging from 10 to 90% and that these IF fractions are reproducible in different mice. For most V(H)s, the IF fraction in pro-B cells approximated 33% and then shifted to the nearly final (mature) B cell value by the cycling pre-B cell stage. The frequency of high in-frame (IF) V(H) usage increased in cycling pre-B cells compared with that in pro-B cells, whereas this did not occur for low IF V(H)s. The IF fraction did not shift as much in BCR-expressing B cells and was minimally affected by L chain usage for most V(H). High IF clan II/III V(H)s share more positively charged CDR2 sequences, whereas high IF clan I J558 CDR2 sequences are diverse. These data indicate that individual V(H)s are subjected to differential selection, that V(H) IF fraction is mainly established through pre-BCR-mediated selection, that it may operate differently in clan I versus II/III V(H)s, and that it has a lasting influence on the Ab repertoire.

Therapeutic targeting of B cells for rheumatic autoimmune diseases

Autoreactive B cells are characterized by their ability to secrete autoantibodies directed against self-peptides. During the last decade, it has become increasingly apparent that B lymphocytes not only produce autoantibodies but also exert important regulatory roles independent of their function as antibody-producing cells. This is especially relevant in the context of autoimmunity, because autoreactive B cells have been shown to possess the ability to activate pathogenic T cells, to produce pro-inflammatory cytokines, and to promote the formation of tertiary lymphoid tissue in target organs. The production of monoclonal antibodies against B-cell-surface molecules has facilitated the characterization of several distinct B lymphocyte subsets. These cell-surface molecules have not only served as useful cell differentiation markers but have also helped to unravel the important biological functions of these cells. Some of these molecules, all of which are expressed on the cell surface, have proven to be effective therapeutic targets. In both animal models and in clinical assays, the efficient elimination of B lymphocytes has been shown to be useful in the treatment of rheumatoid arthritis and other autoimmune diseases. The treatment of most rheumatic autoimmune diseases relies mainly on the use of cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, patients may nonetheless suffer severe adverse events and, in some cases, their relapse rate remains high. The increasing need for safer and more effective drugs along with burgeoning new insights into the pathogenesis of these disorders has fueled interest in biological agents; clinical trials involving the B-cell depletion agent rituximab have been especially promising. This article reviews the current knowledge of B-cell biology and pathogenesis as well as the modern therapeutic approaches for rheumatic autoimmune diseases focusing in particular on the targeting of B-cell-specific surface molecules and on the blocking of B-cell activation and survival.

Elucidation of seventeen human peripheral blood B-cell subsets and quantification of the tetanus response using a density-based method for the automated identification of cell populations in multidimensional flow cytometry data

BACKGROUND

Advances in multiparameter flow cytometry (FCM) now allow for the independent detection of larger numbers of fluorochromes on individual cells, generating data with increasingly higher dimensionality. The increased complexity of these data has made it difficult to identify cell populations from high-dimensional FCM data using traditional manual gating strategies based on single-color or two-color displays.

METHODS

To address this challenge, we developed a novel program, FLOCK (FLOw Clustering without K), that uses a density-based clustering approach to algorithmically identify biologically relevant cell populations from multiple samples in an unbiased fashion, thereby eliminating operator-dependent variability.

RESULTS

FLOCK was used to objectively identify seventeen distinct B-cell subsets in a human peripheral blood sample and to identify and quantify novel plasmablast subsets responding transiently to tetanus and other vaccinations in peripheral blood. FLOCK has been implemented in the publically available Immunology Database and Analysis Portal-ImmPort (http://www.immport.org)-for open use by the immunology research community.

CONCLUSIONS

FLOCK is able to identify cell subsets in experiments that use multiparameter FCM through an objective, automated computational approach. The use of algorithms like FLOCK for FCM data analysis obviates the need for subjective and labor-intensive manual gating to identify and quantify cell subsets. Novel populations identified by these computational approaches can serve as hypotheses for further experimental study.

Autoimmune markers in diabetes

BACKGROUND

Type 1 diabetes (T1DM) results from cell-mediated autoimmune destruction of the β cells of the islets of Langerhans. Autoantibodies directed against the islets are useful clinical tools that allow the recognition and confirmation of β-cell autoimmunity.

CONTENT

In this review we define the term "islet autoantibody," describe the pathogenesis of autoantibody generation, and explain the uses of islet autoantibodies in clinical medicine and in research studies that concern the interruption or prevention of T1DM. We also discuss the biology of islet autoantibodies and their rates of appearance at the time of onset of T1DM and their appearance before the development of T1DM.

SUMMARY

The presence of islet autoantibodies in persons with diabetes confirms an autoimmune etiology. In nondiabetic individuals, islet autoantibodies are strong predictors of the later development of T1DM.

Targeting B cells for the treatment of SLE: the beginning of the end or the end of the beginning?

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease for which therapeutic advances in immunosuppressive and support therapy have significantly improved survival over the last 5 decades. Unfortunately, SLE still carries substantially increased rates of mortality and end stage renal disease which are even more elevated in younger patients. No new drugs have been approved for SLE in over 50 years. Hence, a lot of hope and excitement has been generated by the development of biological agents designed to eliminate B cells either through direct killing (anti-B cell antibodies such as rituximab) or attrition by inhibition of survival (anti-BLyS/BAFF agents such as belimumab). Indeed a strong rationale for targeting B cells in SLE is supported by the major pathogenic roles they play in SLE through both autoantibody production and multiple antibody-independent functions. These hopes, however, have been darted by the failure of two different phase III randomized placebo-controlled trials of rituximab. Yet, clinicians continue to use rituximab off-label with the belief that it provides significant benefit and can rescue patients with disease that is refractory to current modalities. Moreover, recent positive results of two large controlled trials of belimumab have restored confidence that B cell targeting may after all be of benefit in SLE. In this review we discuss the background and rationale for the use of anti-B cell agents in SLE, review the available results, and provide models that could help reconcile the opposing results observed in different studies. These models could also help frame the design and evaluation of current and future B cell therapies.

B cell therapies for rheumatoid arthritis: beyond B cell depletion

Initially suggested by the presence of rheumatoid factor autoantibodies, multiple pathogenic roles for B cells (both antibody-mediated and antibody-independent) in rheumatoid arthritis (RA) now are supported by a growing body of experimental observations and human studies. The pathogenic significance of B cells in this disease also has been established conclusively by the proven benefit of Rituximab-induced B cell depletion in RA patients refractory to tumor necrosis factor (TNF) blockade. This article reviews the rationale for the use of B cell-targeting therapies in RA and discusses the caveats and limitations of indiscriminate B cell depletion as currently applied, ncluding incomplete depletion of pathogenic B cells and elimination of protective B cells. Finally, it presents alternative therapeutic strategies that exploit current knowledge of B cell activation, survival, and differentiation to provide more selective B cell and plasma cell targeting.

G alpha q-containing G proteins regulate B cell selection and survival and are required to prevent B cell-dependent autoimmunity

Survival of mature B cells is regulated by B cell receptor and BAFFR-dependent signals. We show that B cells from mice lacking the G_αq subunit of trimeric G proteins (Gnaq^−/− mice) have an intrinsic survival advantage over normal B cells, even in the absence of BAFF. Gnaq^−/− B cells develop normally in the bone marrow but inappropriately survive peripheral tolerance checkpoints, leading to the accumulation of transitional, marginal zone, and follicular B cells, many of which are autoreactive. Gnaq^−/− chimeric mice rapidly develop arthritis as well as other manifestations of systemic autoimmune disease. Importantly, we demonstrate that the development of the autoreactive B cell compartment is the result of an intrinsic defect in Gnaq^−/− B cells, resulting in the aberrant activation of the prosurvival factor Akt. Together, these data show for the first time that signaling through trimeric G proteins is critically important for maintaining control of peripheral B cell tolerance induction and repressing autoimmunity.

B cells as therapeutic targets in SLE

The use of B-cell targeted therapies for the treatment of systemic lupus erythematosus (SLE) has generated great interest owing to the multiple pathogenic roles carried out by B cells in this disease. Strong support for targeting B cells is provided by genetic, immunological and clinical observations that place these cells at the center of SLE pathogenesis, as initiating, amplifying and effector cells. Interest in targeting B cells has also been fostered by the successful use of similar interventions to treat other autoimmune diseases such as rheumatoid arthritis, and by the initial promise shown by B-cell depletion to treat SLE in early studies. Although the initial high enthusiasm has been tempered by negative results from phase III trials of the B-cell-depleting agent rituximab in SLE, renewed vigor should be instilled in the field by the convergence of the latest results using agents that inhibit B-cell-activating factor (BAFF, also known as BLyS and tumor necrosis factor ligand superfamily, member 13b), further analysis of data from trials using rituximab and greatly improved understanding of B-cell biology. Combined, the available information identifies several new avenues for the therapeutic targeting of B cells in SLE.

Innate pathways to B-cell activation and tolerance

B cells represent an important link between the adaptive and innate immune systems as they express both antigen-specific B-cell receptors (BCRs) as well as various Toll-like receptors (TLRs). Several checkpoints in B-cell development ensure that self-specific cells are eliminated from the mature B-cell repertoire to avoid harmful autoreactive responses. These checkpoints are controlled by BCR-mediated events but are also influenced by TLR-dependent signals from the innate immune system. Additionally, B-cell-intrinsic and extrinsic TLR signaling are critical for inflammatory events required for the clearance of microbial infections. Factors secreted by TLR-activated macrophages or dendritic cells directly influence the fate of protective and autoreactive B cells. Additionally, naive and memory B cells respond differentially to TLR ligands, as do different B-cell subsets. We review here recent literature describing intrinsic and extrinsic effects of TLR stimulation on the fate of B cells, with particular attention to autoimmune diseases.