IL-17-producing B cells combat parasites

The role of B cells in systemic sclerosis

Systemic sclerosis (SSc) is a rare and refractory systemic disease characterized by fibrosis and vasculopathy in the presence of autoimmune abnormalities. While the exact cause of SSc is incompletely understood, the specific autoantibodies identified in SSc are closely linked to disease severity and prognosis, indicating a significant role of autoimmune abnormalities in the pathogenesis of SSc. Although the direct pathogenic mechanisms of autoantibodies in SSc are not fully elucidated, numerous prior investigations have demonstrated the involvement of B cells in the pathogenesis of SSc through various mechanisms. Additionally, several clinical trials have explored the efficacy of B-cell depletion therapy for SSc, with many reporting positive outcomes. However, the role of B cells in SSc pathogenesis is multifaceted, as they can both promote inflammation and exert inhibitory functions. This article provides an overview of the involvement of B cells in SSc development, incorporating the latest research findings.

Th17 Cell and Inflammatory Infiltrate Interactions in Cutaneous Leishmaniasis: Unraveling Immunopathogenic Mechanisms

The inflammatory response during cutaneous leishmaniasis (CL) involves immune and non-immune cell cooperation to contain and eliminate Leishmania parasites. The orchestration of these responses is coordinated primarily by CD4+ T cells; however, the disease outcome depends on the Th cell predominant phenotype. Although Th1 and Th2 phenotypes are the most addressed as steers for the resolution or perpetuation of the disease, Th17 cell activities, especially IL-17 release, are recognized to be vital during CL development. Th17 cells perform vital functions during both acute and chronic phases of CL. Overall, Th17 cells induce the migration of phagocytes (neutrophils, macrophages) to the infection site and CD8+ T cells and NK cell activation. They also provoke granzyme and perforin secretion from CD8+ T cells, macrophage differentiation towards an M2 phenotype, and expansion of B and Treg cells. Likewise, immune cells from the inflammatory infiltrate have modulatory activities over Th17 cells involving their differentiation from naive CD4+ T cells and further expansion by generating a microenvironment rich in optimal cytokines such as IL-1β, TGF-β, IL-6, and IL-21. Th17 cell activities and synergies are crucial for the resistance of the infection during the early and acute stages; however, if unchecked, Th17 cells might lead to a chronic stage. This review discusses the synergies between Th17 cells and the inflammatory infiltrate and how these interactions might destine the course of CL.

B cells promote granulomatous inflammation during chronic Mycobacterium tuberculosis infection in mice

The current study reveals that in chronic TB, the B cell-deficient μMT strain, relative to wild-type (WT) C57BL/6 mice, displays in the lungs lower levels of inflammation that are associated with decreased CD4+ T cell proliferation, diminished Th1 response, and enhanced levels of interleukin (IL)-10. The latter result raises the possibility that B cells may restrict lung expression of IL-10 in chronic TB. These observations are recapitulated in WT mice depleted for B cells using anti-CD20 antibodies. IL-10 receptor (IL-10R) blockade reverses the phenotypes of decreased inflammation and attenuated CD4+ T cell responses in B cell-depleted mice. Together, these results suggest that in chronic murine TB, B cells, by virtue of their capacity to restrict expression of the anti-inflammatory and immunosuppressive IL-10 in the lungs, promote the development of a robust protective Th1 response, thereby optimizing anti-TB immunity. This vigorous Th1 immunity and restricted IL-10 expression may, however, allow the development of inflammation to a level that can be detrimental to the host. Indeed, decreased lung inflammation observed in chronically infected B cell-deficient mice, which exhibit augmented lung IL-10 levels, is associated with a survival advantage relative to WT animals. Collectively, the results reveal that in chronic murine TB, B cells play a role in modulating the protective Th1 immunity and the anti-inflammatory IL-10 response, which results in augmentation of lung inflammation that can be host-detrimental. Intriguingly, in tuberculous human lungs, conspicuous B cell aggregates are present in close proximity to tissue-damaging lesions manifesting necrosis and cavitation, suggesting the possibility that in human TB, B cells may contribute to the development of exacerbated pathology that is known to promote transmission. Since transmission is a major hindrance to TB control, investigating into whether B cells can shape the development of severe pulmonic pathological responses in tuberculous individuals is warranted.

IL-17A expression by both T cells and non-T cells contribute to HSV-IL-2-induced CNS demyelination

Previously we reported that a recombinant HSV-1 expressing murine IL-2 (HSV-IL-2) causes CNS demyelination in different strains of mice and in a T cell-dependent manner. Since TH17 cells have been implicated in CNS pathology, in the present study, we looked into the effects of IL-17A-/- and three of its receptors on HSV-IL-2-induced CNS demyelination. IL-17A-/- mice did not develop CNS demyelination, while IL-17RA-/-, IL-17RC-/-, IL-17RD-/- and IL-17RA-/-RC-/- mice developed CNS demyelination. Adoptive transfer of T cells from wild-type (WT) mice to IL-17A-/- mice or T cells from IL-17A-/- mice to Rag-/- mice induced CNS demyelination in infected mice. Adoptive T cell experiments suggest that both T cells and non-T cells expressing IL-17A contribute to HSV-IL-2-induced CNS demyelination with no difference in the severity of demyelination between the two groups of IL-17A producing cells. IL-6, IL-10, or TGFβ did not contribute to CNS demyelination in infected mice. Transcriptome analysis between IL-17A-/- brain and spinal cord of infected mice with and without T cell transfer from WT mice revealed that "neuron projection extension involved in neuron projection guidance" and "ensheathment of neurons" pathways were associated with CNS demyelination. Collectively, the results indicate the importance of IL-17A in CNS demyelination and the possible involvement of more than three of IL-17 receptors in CNS demyelination.

Vaccination with Mycoplasma pneumoniae membrane lipoproteins induces IL-17A driven neutrophilia that mediates Vaccine-Enhanced Disease

Bacterial lipoproteins are an often-underappreciated class of microbe-associated molecular patterns with potent immunomodulatory activity. We previously reported that vaccination of BALB/c mice with Mycoplasma pneumoniae (Mp) lipid-associated membrane proteins (LAMPs) resulted in lipoprotein-dependent vaccine enhanced disease after challenge with virulent Mp, though the immune responses underpinning this phenomenon remain poorly understood. Herein, we report that lipoprotein-induced VED in a mouse model is associated with elevated inflammatory cytokines TNF-α, IL-1β, IL-6, IL-17A, and KC in lung lavage fluid and with suppurative pneumonia marked by exuberant neutrophilia in the pulmonary parenchyma. Whole-lung-digest flow cytometry and RNAScope analysis identified multiple cellular sources for IL-17A, and the numbers of IL-17A producing cells were increased in LAMPs-vaccinated/Mp-challenged animals compared to controls. Specific IL-17A or neutrophil depletion reduced disease severity in our VED model—indicating that Mp lipoproteins induce VED in an IL-17A-dependent manner and through exuberant neutrophil recruitment. IL-17A neutralization reduced levels of TNF-α, IL-1β, IL-6, and KC, indicating that IL-17A preceded other inflammatory cytokines. Surprisingly, we found that IL-17A neutralization impaired bacterial clearance, while neutrophil depletion improved it—indicating that, while IL-17A appears to confer both maladaptive and protective responses, neutrophils play an entirely maladaptive role in VED. Given that lipoproteins are found in virtually all bacteria, the potential for lipoprotein-mediated maladaptive inflammatory responses should be taken into consideration when developing vaccines against bacterial pathogens.

Involvement of B cells in the development of systemic sclerosis

Systemic sclerosis (SSc) is a rare intractable systemic disease that causes fibrosis and vasculopathy against a background of autoimmune abnormalities. Although the etiology is not yet fully understood, the type of autoantibodies detected in SSc is closely associated with disease severity and prognosis, supporting that those autoimmune abnormalities play an important role in the pathogenesis of SSc. Although the direct pathogenicity of autoantibodies found in SSc is unknown, many previous studies have shown that B cells are involved in the development of SSc through a variety of functions. Furthermore, a number of clinical studies have been conducted in which B-cell depletion therapy has been tried for SSc, and many of these studies have found B-cell depletion therapy to be effective for SSc. However, the involvement of B cells in pathogenesis is complex, as they not only promote inflammation but also play an inhibitory role. This article outlines the role of B cells in the development of SSc, including the latest research.

Cruzipain Sulfotopes-Specific Antibodies Generate Cardiac Tissue Abnormalities and Favor Trypanosoma cruzi Infection in the BALB/c Mice Model of Experimental Chagas Disease

Trypanosoma cruzi cruzipain (Cz) bears a C-terminal domain (C-T) that contains sulfated epitopes “sulfotopes” (GlcNAc6S) on its unique N-glycosylation site. The effects of in vivo exposure to GlcNAc6S on heart tissue ultrastructure, immune responses, and along the outcome of infection by T. cruzi, were evaluated in a murine experimental model, BALB/c, using three independent strategies. First, mice were pre-exposed to C-T by immunization. C-T-immunized mice (C-T_IM) showed IgG2a/IgG1 <1, induced the production of cytokines from Th2, Th17, and Th1 profiles with respect to those of dC-T_IM, which only induced IL-10 respect to the control mice. Surprisingly, after sublethal challenge, both C-T_IM and dC-T_IM showed significantly higher parasitemia and mortality than the control group. Second, mice exposed to BSA-GlcNAc6S as immunogen (BSA-GlcNAc6S_IM) showed: severe ultrastructural cardiac alterations while BSA-GlcNAc_IM conserved the regular tissue architecture with slight myofibril changes; a strong highly specific humoral-immune-response reproducing the IgG-isotype-profile obtained with C-T_IM; and a significant memory-T-cell-response demonstrating sulfotope-immunodominance with respect to BSA-GlcNAc_IM. After sublethal challenge, BSA-GlcNAc6S_IM showed exacerbated parasitemias, despite elevated IFN-γ levels were registered. In both cases, the abrogation of ultrastructural alterations when using desulfated immunogens supported the direct involvement of sulfotopes and/or indirect effect through their specific antibodies, in the induction of tissue damage. Finally, a third strategy using a passive transference of sulfotope-specific antibodies (IgG-GlcNAc6S) showed the detrimental activity of IgG-GlcNAc6S on mice cardiac tissue, and mice treated with IgG-GlcNAc6S after a sublethal dose of T. cruzi, surprisingly reached higher parasitemias than control groups. These findings confirmed the indirect role of the sulfotopes, via their IgG-GlcNAc6S, both in the immunopathogenicity as well as favoring T. cruzi infection.

Gammaherpesvirus Usurps Host IL-17 Signaling To Support the Establishment of Chronic Infection

Gammaherpesviruses establish lifelong infections in a majority of humans and are associated with B cell lymphomas. IL-17A is a host cytokine that plays a well-established role in the clearance of bacterial and fungal infections; however, the role of IL-17A in viral infections is poorly understood.

Gammaherpesviruses establish lifelong infection and are associated with a variety of cancers, including B cell lymphomas. These viruses manipulate the B cell differentiation process to establish lifelong infection in memory B cells. Specifically, gammaherpesviruses infect naive B cells and promote entry of both infected and uninfected naive B cells into germinal centers, where the virus usurps rapid proliferation of germinal center B cells to exponentially increase its cellular latent reservoir. In addition to facilitating the establishment of latent infection, germinal center B cells are thought to be the target of viral transformation. In this study, we have uncovered a novel proviral role of host interleukin 17A (IL-17A), a well-established antibacterial and antifungal factor. Loss of IL-17A signaling attenuated the establishment of chronic gammaherpesvirus infection and gammaherpesvirus-driven germinal center response in a route of inoculation-dependent manner. Further, IL-17A treatment directly supported gammaherpesvirus reactivation and de novo lytic infection. This study is the first demonstration of a multifaceted proviral role of IL-17 signaling.

Hypothyroidism impairs the host immune response during the acute phase of Chagas disease

Diseases associated with thyroid hypofunction have been the subject of studies in infectious models, since several authors have demonstrated a pivotal role of iodinated hormones (thyroxine and triiodothyronine) in the modulation of immune effector responses. Using a model of hypothyroidism induced by anti-thyroid drug, we investigated the influence of hypothyroidism in the course of acute Trypanosoma cruzi infection. For this, male Hannover Wistar rats were challenged with methimazole for 21 days (0.02% in drinking water), and water for control counterparts. After confirmation of the hypothyroidism, rats were intraperitoneally challenged with 1x10⁵ blood trypomastigotes of the Y strain of T. cruzi. Our findings suggest that hypothyroidism impairs animal weight gain, but does not affect the health of essential organs. Interestingly, infected hypothyroid animals had a significant increase in thymic cell death, with consequent drop in lymphocyte frequency in whole blood (evaluated on the 11th day of infection). Analyzing the percentage of immune cells in the spleen, we found a strong influence of hypothyroidism as a negative regulator of B cells, and antigenic ability of macrophages (RT1b expression) in the course of the experimental chagasic infection. Enhanced serum IL-17A concentration was induced by T. cruzi infection, but hypothyroidism impaired the production of this mediator as seen in infected hypothyroid animals. Taken together, our work suggests for the first time that hypothyroidism may adversely interfere with the modulation of effective immunity in the early phase of Chagas' disease.

Innate-like B cell subsets during immune responses: Beyond antibody production

B lymphocytes are recognized for their crucial role in the adaptive immunity since they represent the only leukocyte lineage capable of differentiating into Ab-secreting cells. However, it has been demonstrated that these lymphocytes can exert several Ab-independent functions, including engulfing and processing Ags for presentation to T cells, secreting soluble mediators, providing co-stimulatory signals, and even participating in lymphoid tissues development. Beyond that, several reports claiming the existence of multiple B cell subsets contributing directly to innate immune responses have appeared. These "innate-like" B lymphocytes, whose phenotype, development pathways, tissue distribution, and functions are in most cases notoriously different from those of conventional B cells, are crucial to early protective responses against pathogens by exerting "crossover" defensive strategies that blur the established boundaries of innate and adaptive branches of immunity. Examples of these mechanisms include the rapid secretion of the polyspecific natural Abs, increased susceptibility to innate receptors-mediated activation, cytokine secretion, downstream priming of other innate cells, usage of specific variable immunoglobulin gene-segments, and other features. As these new insights emerge, it is becoming preponderant to redefine the functionality of B cells beyond their classical adaptive-immune tasks.

The Response of IL-17-Producing B Cells to ArtinM Is Independent of Its Interaction with TLR2 and CD14

ArtinM, a d-mannose-binding lectin from Artocarpus heterophyllus, activates antigen-presenting cells by recognizing Toll-like receptor (TLR)2 and cluster of differentiation (CD)14 N-glycans, induces cytokine production, and promotes type 1 T helper (Th1) immunity, a process that plays an assisting role in the combat against fungal infections. We recently demonstrated that ArtinM stimulates CD4⁺ T cells to produce interleukin (IL)-17 through direct interaction with CD3. Here, we further investigated the effects of ArtinM on the production of IL-17 by B cell activation. We showed that ArtinM activates murine B cells, increasing IL-17 and IL-12p40 production. The direct effect of ArtinM was sufficient to induce IL-17 production in B cells, and we did not find differences in the levels of IL-17 between the B cells purified from the wild-type (WT) and knockout (KO) mice for TLR2 or CD14 in the presence of ArtinM. Thus, the effects of ArtinM on splenic B cells through carbohydrate recognition may contribute to Th17 immunity; however, the mechanism involved is not associated with the interaction of ArtinM with TLR2 and CD14. The current work represents a pioneering effort in the understanding of the induction of IL-17 by lectins in B cells.

Interleukin 17A as a good predictor of the severity of Mycoplasma pneumoniae pneumonia in children

Early distinction between severe Mycoplasma pneumoniae pneumonia (MPP) and mild MPP is still difficult. The aim of this study was to analyze cytokines in bronchoalveolar lavage fluid (BALF) and explore predicting factors of severe MPP in children. Retrospective analysis was performed on 150 children with MPP or bronchial foreign body (FB) admitted in our hospital. The mRNA levels of IL17A were found significantly lower in severe MPP group comparing with mild MPP group or FB group. However, no significant difference was found in the levels of IL4, IL10 or interferon beta1 (IFNβ1) between the two groups. Receiver operator characteristic (ROC) curve analysis showed that IL17A can be used to distinguish severe MPP from mild MPP. These results were confirmed in a validation cohort including 40 MPP children from another hospital. IL17A levels were correlated with some clinical characters, such as refractoriness and pleural effusion. Lower IL17A levels were more likely to be found in refractory MPP children or in MPP children with pleural effusion. Moreover, the protein levels of IL17A in BALF were also found greatly decreased in children with severe MPP. Thus, decreased IL17A levels in BALF may be a valuable biomarker to identify severe MPP in children.

The excretory-secretory products of Echinococcus granulosus protoscoleces directly regulate the differentiation of B10, B17 and Th17 cells

Background

Excretory-secretory products (ESPs) released by helminths are well-known to regulate T cell responses in the host. However, their direct influence in the differentiation of naïve T cells, and especially B cells, remains largely unknown. This study investigated the effects of Echinococcus granulosus protoscoleces ESPs (EgPSC-ESPs) on the differentiation of IL-10-producing B cells (B10), IL-17A-producing B cells (B17) and Th17 cells.

Methods

BALB/c mice injected with EgPSC were used to evaluate the in vivo profiles of B10, B17 and Th17 cells. In vitro purified CD19⁺ B and naïve CD4⁺ T cells were cultured in the presence of native, heat-inactivated or periodate-treated EgPSC-ESPs, and the differentiation of these cell subsets were compared.

Results

In contrast to the control group, infected mice showed higher frequencies of B10, B17 and Th17 cells, and higher levels of IL-10 and IL-17A in the sera. Interestingly, B17 cells were first identified to express CD19⁺CD1d^high. In vitro, B cells cultured with native ESPs exhibited a higher percentage of B10 cells but lower percentage of B17 and Th17 cells compared to the PBS group. Moreover, the relative expression of IL-10 and IL-17A mRNA were consistent with the altered frequencies. However, ESPs subjected to heat-inactivation or periodate treatment exhibited an inverse effect on the induction of these cell subsets.

Conclusions

Our findings indicate that ESPs released by EgPSC can directly regulate the differentiation of B10, B17 and Th17 cells, which appear to be heat-labile and carbohydrate-dependent.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2263-9) contains supplementary material, which is available to authorized users.

The role of interleukin 17-mediated immune response in Chagas disease: High level is correlated with better left ventricular function

Interleukin 17A (IL-17A) has been associated with protective rather than pathogenic response in Chagas disease (ChD). However, it is not established whether or not IL-17A-mediated immune response is correlated with patient’s left ventricular (LV) function in ChD. To address this question we have gathered cardiac functional parameters from ChD patients and analysed the possible relationship between their plasma IL-17A levels and LV function. Plasma IL-17A levels were measured by BD Cytometric Bead Array (CBA) in 240 patients with positive specific serology for Trypanosoma cruzi (T. cruzi) grouped as indeterminate (IND) and Chagas cardiomyopathy (CARD) forms. The levels of IL-17A in ChD patients were compared with 32 healthy individuals, mean age of 39 years, 50% male, that were also included as a control group (non-infected [NI]). The overall mean age of ChD patients was 46 years and 52% were male. The IND group included 95 asymptomatic patients, with ages ranging from 27 to 69 years (mean of 43 years), and 42.1% of them were male. The CARD group included 145 patients, which 58.6% were male, with ages ranging from 23 to 67 years (mean of 49). The IND group presented substantially higher levels of IL-17A, median of 26.16 (3.66–48.33) as compared to both the CARD group, median of 13.89 (3.87–34.54) (P <0.0001), and the NI group, median of 10.78 (6.23–22.26) (P <0.0001). The data analysis demonstrated that the IND group comprises a significantly greater proportion (P <0.001) of high IL-17A producers (52.6%, 50 of 95 subjects) than do the other groups. A significant direct correlation was verified between IL-17A levels and cardiac function expressed by LV ejection fraction (LVEF), LV diastolic diameter (LVDd), and body surface area (BSA)-indexed LVDd as well as ratio of the early diastolic transmitral flow velocity to early diastolic mitral annular velocity (E/e’) in both groups. We demonstrated that plasma IL-17A levels has an accurate sensitivity and specificity to predict heart failure in serology-positive patients and might be a useful parameter to distinguish patients with or without cardiac impairment. This study indicates a consistent relationship between high expression of IL-17A and better LV in human chronic ChD. Our data raise the possibility that IL-17A plays an important immunomodulatory role in the chronic phase of ChD and might be involved in protection against myocardial damage.

B cell abnormalities and therapeutic strategies in systemic sclerosis

One of the major roles of B cells is to generate antibodies to specific antigens. Secreted antibodies are the principal molecules involved in humoral immunity, with the capacity not only to neutralize pathogens, but also to enhance their elimination by activating phagocytosis or complement proteins. Recently, it has been highlighted that B cells exert important regulatory roles independent of their antibody producing function. These roles include efficiently presenting antigens to the T cells, secreting cytokines, and inducing immune cell differentiation. Thus, B cells have emerged as cells that play crucial roles in immune systems in addition to producing antibodies. Systemic sclerosis (SSc) is characterized by autoimmunity and tissue fibrosis of several organs. Although the pathogenic relationship between systemic autoimmunity and the clinical manifestations of SSc remains unknown, SSc patients display a variety of abnormal immune activation including the production of disease-specific autoantibodies. Previous studies have demonstrated that immune cells, mainly including B cells, play a critical role in systemic autoimmunity and disease expression, though the role of autoimmunity in generating the clinical and pathologic phenotype in SSc remains uncertain. SSc patients have B cell abnormalities characterized by chronic hyper-reactivity of memory B cells. Although distinct subsets of autoantibodies do not have a proven pathogenic role, they are selectively associated with unique disease manifestations. To date, the treatment of SSc has largely relied on cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, these patients may still suffer severe adverse events and refractory disease to conventional immunosuppressive therapies. Recently, clinical trials involving the chimeric monoclonal antibody rituximab have raised high expectations. B cell depleting therapy with rituximab offers a promising treatment for the rheumatic autoimmune diseases including SSc. This article reviews the current knowledge of B cell biology and pathogenesis in SSc as well as the therapeutic approaches focusing on the targeting of B cell specific surface molecules and on the blocking of B cell activation and survival.

Bifidobacterium breve attenuates murine dextran sodium sulfate-induced colitis and increases regulatory T cell responses

While some probiotics have shown beneficial effects on preventing or treating colitis development, others have shown no effects. In this study, we have assessed the immunomodulating effects of two probiotic strains, Lactobacillus rhamnosus (L. rhamnosus) and Bifidobacterium breve (B. breve) on T cell polarization in vitro, using human peripheral blood mononuclear cells (PBMC), and in vivo, using murine dextran sodium sulfate (DSS) colitis model. With respect to the latter, the mRNA expression of T cell subset-associated transcription factors and cytokines in the colon was measured and the T helper type (Th) 17 and regulatory T cell (Treg) subsets were determined in the Peyer's patches. Both L. rhamnosus and B. breve incubations in vitro reduced Th17 and increased Th2 cell subsets in human PBMCs. In addition, B. breve incubation was also able to reduce Th1 and increase Treg cell subsets in contrast to L. rhamnosus. In vivo intervention with B. breve, but not L. rhamnosus, significantly attenuated the severity of DSS-induced colitis. In DSS-treated C57BL/6 mice, intervention with B. breve increased the expression of mRNA encoding for Th2- and Treg-associated cytokines in the distal colon. In addition, intervention with B. breve led to increases of Treg and decreases of Th17 cell subsets in Peyer's patches of DSS-treated mice. B. breve modulates T cell polarization towards Th2 and Treg cell-associated responses in vitro and in vivo. In vivo B. breve intervention ameliorates DSS-induced colitis symptoms and this protective effect may mediated by its effects on the T-cell composition.

The immune potential and immunopathology of cytokine-producing B cell subsets: a comprehensive review

B lymphocytes are generally recognized for their potential to mediate humoral immunity by producing different antibody isotypes and being involved in opsonization and complement fixation. Nevertheless, the non-classical, antibody-independent immune potential of B cell subsets has attracted much attention especially in the past decade. These B cells can release a broad variety of cytokines (such as IL-2, IL-4, IL-6, IL-10, IL-17, IFN-α, IFN-γ, TNF-α, TGF-β, LT), and can be classified into distinct subsets depending on the particular cytokine profile, thus emerging the concept of cytokine-producing B cell subsets. Although there is still controversy surrounding the key cell surface markers, intracellular factors and cellular origins of cytokine-producing B cell subsets, accumulating evidence indicates that these B cells are endowed with great potential to regulate both innate and adaptive arms of immune system though releasing cytokines. On the one hand, they promote immune responses through mounting Th1/Th2/Th17 and neutrophil response, inducing DC maturation and formation of lymphoid structures, increasing NK cell and macrophage activation, enhancing development of themselves and sustaining antibody production. On the other hand, they can negatively regulate immune responses by suppressing Th cell responses, inhibiting Tr1 cell and Foxp3(+) Treg differentiation, impairing APC function and pro-inflammatory cytokine release by monocytes, and inducing CD8(+) T cell anergy and CD4(+) T cell apoptosis. Therefore, cytokine-producing B cell subsets have multifunctional functions in health and diseases, playing pathologic as well as protective roles in autoimmunity, infection, allergy, and even malignancy. In this review, we revisit the history of discovering cytokine-producing B cells, describe the identification of cytokine-producing B cell subsets, introduce the origins of cytokine-producing B cell subsets as well as molecular and cellular mechanisms for their differentiation, and summarize the recent progress made toward understanding the unexpectedly complex and potentially opposing roles of cytokine-producing B cells in immunological disorders.

B cells contribute to heterogeneity of IL-17 producing cells in rheumatoid arthritis and healthy controls

Secretion of the proinflammatory cytokine Interleukin-17A (IL-17A) is the hallmark of a unique lineage of CD4 T cells designated Th17 cells, which may play a crucial role in the pathogenesis of rheumatoid arthritis (RA) and many autoimmune diseases. Recently, IL-17-producing cells other than T cells have been described, including diverse innate immune cells. Here, we show that the cellular sources of IL-17A in RA include a significant number of non-T cells. Multicolour fluorescence analysis of IL-17-expressing peripheral blood mononuclear cells (PBMC) revealed larger proportions of IL-17⁺CD3^- non-T cells in RA patients than in healthy controls (constitutive, 13.6% vs. 8.4%, and after stimulation with PMA/ionomycin 17.4% vs. 7.9% p < 0.001 in both cases). The source of IL-17 included CD3^-CD56⁺ NK cells, CD3^-CD14⁺ myeloid cells as well as the expected CD3⁺CD4⁺ Th17 cells and surprisingly a substantial number of CD3^-CD19⁺ B cells. The presence of IL-17A-expressing B cells was confirmed by specific PCR of peripheral MACS-sorted CD19⁺ B cells, as well as by the analysis of different EBV-transformed B cell lines. Here we report for the first time that in addition to Th17 cells and different innate immune cells B cells also contribute to the IL-17A found in RA patients and healthy controls.