Treatment of collagen‐induced arthritis by Natura‐α via regulation of Th‐1/Th‐17 responses

Cytokines and CD4⁺ Th cells play a crucial role in the pathogenesis of rheumatoid arthritis. Among the Th populations, Th‐1 and Th‐17 have been described as pathogenic in collagen‐induced arthritis (CIA) whereas Th‐2 and Treg were found to have protective effects. The objective of this study was to examine the affect of Natura‐α, a newly developed cytokine regulator, on CIA and on Th cell development. Natura‐α treatment was administered before or during arthritis induction. Anti‐type II collagen antibodies and cytokine expression were evaluated by ELISA. Emergence of CD4⁺CD25⁺Foxp3⁺ T cells was assessed by flow cytometry. Th‐17 differentiation of naive CD4 T cells was assessed in cultures with anti‐CD3 and anti‐CD28. We showed that Natura‐α both prevented and treated CIA. We further demonstrated that in vivo treatment with Natura‐α inhibited IL‐17 production and anti‐type II collagen IgG development. We showed in vitro, using an APC‐free system, that Natura‐α acted directly on differentiating T cells and inhibiting the formation of Th‐1 and Th‐17 cells but did not affect Th‐2 cells. Since Natura‐α inhibits a large spectrum of important pathogenic factors in CIA, it may provide a new and powerful approach to the treatment of rheumatoid arthritis and other inflammatory diseases.     

APRIL (TNFSF13) regulates collagen‐induced arthritis,IL‐17 production and Th2 response

A proliferation‐inducing ligand (APRIL or TNFSF13) shares receptors with B‐cell activation factor of the TNF family (BAFF) on B and T cells. Although much is known about the function of APRIL in B cells, its role in T cells remains unclear. Blocking both BAFF and APRIL suggested that BAFF and/or APRIL contributed to collagen‐induced arthritis (CIA); however, the role of APRIL alone in CIA remained unresolved. We show here that, in vitro, our newly generated APRIL^?/? mice exhibited increased T‐cell proliferation, enhanced Th2 cytokine production under non‐polarizing conditions, and augmented IL‐13 and IL‐17 production under Th2 polarizing conditions. Upon immunization with OVA and aluminum potassium sulfate, APRIL^?/? mice responded with an increased antigen‐specific IgG1 response. We also show that in APRIL^?/? mice, the incidence of CIA was significantly reduced compared with WT mice in parallel with diminished levels of antigen‐specific IgG2a autoantibody and IL‐17 production. Our data indicate that APRIL plays an important role in the regulation of cytokine production and that APRIL‐triggered signals contribute to arthritis. Blockade of APRIL thus may be a valuable adjunct in the treatment of rheumatoid arthritis.     

The choice of adjuvant determines the cytokine profile of T cells in proteoglycan‐induced arthritis but does not influence disease severity

Rheumatoid arthritis (RA) is a debilitating autoimmune disease characterized by chronic inflammation of the synovial joints. Collagen‐induced arthritis (CIA) and proteoglycan‐induced arthritis (PGIA) are mouse models of inflammatory arthritis; CIA is a T helper type 17 (Th17) ‐dependent disease that is induced with antigen in complete Freund's adjuvant, whereas PGIA is Th1‐mediated and is induced using antigen in dimethyldioctadecyl‐ammonium bromide (DDA) as an adjuvant. To investigate whether the type of adjuvant determines the cytokine profile of the pathogenic T cells, we have compared the effect of CFA and DDA on T‐cell responses in a single arthritis model. No differences in incidence or disease severity between aggrecan‐T‐cell receptor transgenic mice immunized with aggrecan in either CFA or DDA were observed. Immunization with CFA resulted in a higher proportion of Th17 cells, whereas DDA induced more Th1 cells. However, the levels of interleukin‐17 (IL‐17) produced by T cells isolated from CFA‐immunized mice after antigen‐specific stimulation were not significantly different from those found in DDA‐immunized mice, indicating that the increased proportion of Th17 cells did not result in significantly higher ex vivo IL‐17 levels. Hence, the choice of adjuvant can affect the overall proportions of Th1 and Th17 cells, without necessarily affecting the level of cytokine production or disease incidence and severity.     

Neutrophil extracellular traps exacerbate Th1‐mediated autoimmune responses in rheumatoid arthritis by promoting DC maturation

Aberrant formation of neutrophil extracellular traps (NETs) is a key feature in rheumatoid arthritis (RA) and plays a pivotal role in disease pathogenesis. However, the mechanism through which NETs shape the autoimmune response in RA remains elusive. In this study, we demonstrate that inhibition of peptidylarginine deiminases activity in collagen‐induced arthritis (CIA) mouse model significantly reduces NET formation, attenuates clinical disease activity, and prevents joint destruction. Importantly, peptidylarginine deiminase 4 blocking markedly reduces the frequency of collagen‐specific IFN‐γ‐producing T helper 1 (Th1) cells in the draining lymph nodes of immunized mice. Exposure of dendritic cells (DCs) to CIA‐derived NETs induces DC maturation characterized by significant upregulation of costimulatory molecules, as well as elevated secretion of IL‐6. Moreover, CIA‐NET‐treated DCs promote the induction of antigen‐specific Th1 cells in vitro. Finally, NETs from RA patients show an increased potential to induce the maturation of DCs from healthy individuals, corroborating the findings obtained in CIA mouse model. Collectively, our findings delineate an important role of NETs in the induction and expansion of Th1 pathogenic cells in CIA through maturation of DCs and reveal a novel role of NETs in shaping the RA‐autoimmune response that could be exploited therapeutically.     

Clinical efficacy of a new CD28‐targeting antagonist of T cell co‐stimulation in a non‐human primate model of collagen‐induced arthritis

T cells have a central pathogenic role in the aetiopathogenesis of rheumatoid arthritis (RA), and are therefore a favoured target of immunotherapy aiming at physical or functional elimination. Here we report an efficacy test of FR104, a new co‐stimulation inhibitor directly targeting CD28 on T cells, in a translationally relevant model, the rhesus monkey model of collagen‐induced arthritis (CIA). As a relevant comparator we used abatacept [cytotoxic T lymphocyte antigen immunoglobulin (CTLA Ig)], an antagonist of CTLA‐4 binding to CD80/86 clinically approved for treatment of RA. Treatment with either compound was started at the day of CIA induction. Although FR104 previously demonstrated a higher control of T cell responses in vitro than abatacept, both compounds were equally potent in the suppression of CIA symptoms and biomarkers, such as the production of C‐reactive protein (CRP) and interleukin (IL)‐6 and anti‐collagen type II (CII) serum antibody (IgM/IgG). However, in contrast to abatacept, FR104 showed effective suppression of CII‐induced peripheral blood mononuclear cell (PBMC) proliferation. The current study demonstrates a strong potential of the new selective CD28 antagonist FR104 for treatment of RA.     

Human α1‐antitrypsin modifies B‐lymphocyte responses during allograft transplantation

B‐lymphocyte activities are associated with allograft rejection. Interleukin‐10 (IL‐10) ‐expressing B cells, however, exhibit regulatory attributes. Human α1‐antitrypsin (hAAT), a clinically available anti‐inflammatory circulating glycoprotein that rises during acute‐phase responses, promotes semi‐mature dendritic cells and regulatory T (Treg) cells during alloimmune responses. Whether B lymphocytes are also targets of hAAT activity has yet to be determined. Here, we examine whether hAAT modulates B‐cell responses. In culture, hAAT reduced the lipopolysaccharide‐stimulated Ki‐67⁺ B‐cell population, IgM release and surface CD40 levels, but elevated IL‐10‐producing cells 1.5‐fold. In CD40 ligand‐stimulated cultures, hAAT promoted a similar trend; reduction in the Ki‐67⁺ B‐cell population and in surface expression of CD86, CD80 and MHCII. hAAT increased interferon‐γ‐stimulated macrophage B‐cell activating factor (BAFF) secretion, and reduced BAFF‐receptor levels. Draining lymph nodes of transgenic mice that express circulating hAAT (C57BL/6 background) and that received skin allografts exhibited reduced B‐lymphocyte activation compared with wild‐type recipients. BSA‐vaccinated hAAT transgenic mice exhibited 2.9‐fold lower BSA‐specific IgG levels, but 2.3‐fold greater IgM levels, compared with wild‐type mice. Circulating Treg cells were 1.3‐fold greater in transgenic hAAT mice, but lower in B‐cell knockout (BKO) and chimeric hAAT–BKO mice, compared with wild‐type mice. In conclusion, B cells are cellular targets of hAAT. hAAT‐induced Treg cell expansion appears to be B‐cell‐dependent. These changes support the tolerogenic properties of hAAT during immune responses, and suggest that hAAT may be beneficial in pathologies that involve excessive B‐cell responses.     

Interleukin‐27 suppresses osteoclastogenesis via induction of interferon‐γ

Interleukin (IL)‐27 is a heterodimeric cytokine that is known to have both stimulatory and inhibitory functions during immune responses. We investigated the effects of IL‐27 on arthritis and bone erosion in the murine collagen‐induced arthritis (CIA) model. We demonstrate that the inhibitory effect of IL‐27 on osteoclastogenesis is associated with interferon‐γ (IFN‐γ) production by using an IFN‐γ knockout mouse model. The IL‐27‐Fc was injected into both CIA and IFN‐γ‐deficient mice. The effects of IL‐27‐Fc on osteoclast differentiation were evaluated both in vitro and in vivo. The IL‐27‐Fc‐injected mice showed significantly lower arthritis indices and fewer tartrate‐resistant acid‐phosphatase‐positive osteoclasts in their joint tissues than untreated mice. Interleukin‐27 inhibited osteoclastogenesis from bone marrow‐derived mononuclear cells in vitro, which was counteracted by the addition of anti‐IFN‐γ antibody. The IL‐27‐Fc did not affect arthritis in IFN‐γ knockout mice. Interleukin‐27 also suppressed osteoclast differentiation in human and intriguingly, it could promote the expression of IFN‐γ on priming osteoclasts. These results imply that IL‐27 suppressed the generation of CIA and osteoclastogenesis, which were mediated by the induction of IFN‐γ.     

CARD11 blockade suppresses murine collagen‐induced arthritis via inhibiting CARD11/Bcl10 assembly and T helper type 17 response

The scaffold protein caspase recruitment domain‐containing protein 11 (CARD11) is implicated in the regulation of inflammation and autoimmunity. The present study aimed to explore the role of CARD11 in the pathogenesis of rheumatoid arthritis (RA). Mice with collagen‐induced arthritis (CIA) were treated with either CARD11‐targeted interfering RNA (CARD11 siRNA) or control siRNA by intraperitoneal injection every 3 days after CIA establishment. The clinical score of arthritis was recorded every other day. Synovial inflammation and cartilage erosion were evaluated by histology and microcomputed tomography (micro‐CT). Serum anti‐type II collagen (anti‐CII) antibodies and cytokines were measured by enzyme‐linked immunosorbent assay (ELISA). The CARD11/Bcl10 formation and nuclear factor‐kappa B (NF‐κB) activation was assessed by immunoprecipitation and immunoblotting, and the percentage of T helper type 17 (Th17) cells was determined by flow cytometry. Systemic administration of CARD11 siRNA significantly reduced the clinical score of CIA severity. As indicated by the histology, joint inflammation and destruction were attenuated by CARD11 siRNA treatment. Micro‐CT demonstrated less severe joint destruction in CARD11 siRNA‐treated mice than in control mice. CARD11 siRNA treatment resulted in inhibition of CARD11/Bcl10 formation and the subsequent NF‐κB activation. In addition, treatment with CARD11 siRNA resulted in a pronounced decrease in proinflammatory cytokines interleukin (IL)‐1β, IL‐6 and IL‐17. Serum anti‐CII antibody and the percentage of Th17 cells were also significantly reduced. CARD11 is involved in the pathogenesis of CIA by formation of the CARD11/Bcl10 complex and enhancement of the Th17 cell response. Targeting CARD11 provides a novel research direction in the development of therapeutic strategies for RA.     

B‐cell‐derived IL‐10 does not vitally contribute to the clinical course of glomerulonephritis

IL‐10‐secreting regulatory B cells have been postulated as negative mediators of inflammation. However, their impact on immune‐mediated diseases requires further investigation. We recently found that IL‐10‐secreting B cells infiltrate the kidney during crescentic glomerulonephritis (GN). We therefore studied the function of B‐cell‐derived IL‐10 in light of the potential risks associated with increasingly used B‐cell depleting therapies. Lack of IL‐10 production by B cells, however, did not influence acute or adaptively mediated progressive renal injury in terms of renal function and histological damage in the nephrotoxic nephritis model of GN. Renal leukocyte infiltration and cytokine expression were similar apart from increased macrophages in mice lacking B‐cell‐derived IL‐10. Systemic immune responses as assessed by cytokine production, leukocyte composition, proliferation, and activation were indistinguishable, while production and renal deposition of Ag‐specific IgG were mildly impaired in the absence of B‐cell‐produced IL‐10. Importantly, detailed analysis of systemic and renal regulatory T cells did not show any differences between nephritic mice bearing IL‐10‐deficient B cells and WT controls. Finally, studies in reporter mice revealed that B cells are only a minor source of systemic IL‐10. In summary, our data reveal that endogenous B‐cell‐derived IL‐10 does not play a major role in the nephrotoxic nephritis model of crescentic GN.     

IL‐6: Regulator of Treg/Th17 balance

IL‐6 is a pleiotropic cytokine involved in the physiology of virtually every organ system. Recent studies have demonstrated that IL‐6 has a very important role in regulating the balance between IL‐17‐producing Th17 cells and regulatory T cells (Treg). The two T‐cell subsets play prominent roles in immune functions: Th17 cell is a key player in the pathogenesis of autoimmune diseases and protection against bacterial infections, while Treg functions to restrain excessive effector T‐cell responses. IL‐6 induces the development of Th17 cells from naïve T cells together with TGF‐β; in contrast, IL‐6 inhibits TGF‐β‐induced Treg differentiation. Dysregulation or overproduction of IL‐6 leads to autoimmune diseases such as multiple sclerosis (MS) and rheumatoid arthritis (RA), in which Th17 cells are considered to be the primary cause of pathology. Given the critical role of IL‐6 in altering the balance between Treg and Th17 cells, controlling IL‐6 activities is potentially an effective approach in the treatment of various autoimmune and inflammatory diseases. Here, we review the role of IL‐6 in regulating Th17/Treg balance and describe the critical functions of IL‐6 and Th17 in immunity and immune‐pathology.     

IL‐17‐producing CD4+ T cells contribute to the loss of B‐cell tolerance in experimental autoimmune myasthenia gravis

The role of Th17 cells in the pathogenesis of autoantibody‐mediated diseases is unclear. Here, we assessed the contribution of Th17 cells to the pathogenesis of experimental autoimmune myasthenia gravis (EAMG), which is induced by repetitive immunizations with Torpedo californica acetylcholine receptor (tAChR). We show that a significant fraction of tAChR‐specific CD4⁺ T cells is producing IL‐17. IL‐17^ko mice developed fewer or no EAMG symptoms, although the frequencies of tAChR‐specific CD4⁺ T cells secreting IL‐2, IFN‐γ, or IL‐21, and the percentage of FoxP3⁺ T_reg cells were similar to WT mice. Even though the total anti‐tAChR antibody levels were equal, the complement fixating IgG2b subtype was reduced in IL‐17^ko as compared to WT mice. Most importantly, pathogenic anti‐murine AChR antibodies were significantly lower in IL‐17^ko mice. Furthermore, we confirmed the role of Th17 cells in EAMG pathogenesis by the reconstitution of TCR β/δ^ko mice with WT or IL‐17^ko CD4⁺ T cells. In conclusion, we show that the level of IgG2b and the loss of B‐cell tolerance, which results in pathogenic anti‐murine AChR‐specific antibodies, are dependent on IL‐17 production by CD4⁺ T cells. Thus, we describe here for the first time how Th17 cells are involved in the induction of classical antibody‐mediated autoimmunity.     

B‐type suppression: A role played by “regulatory B cells” or “regulatory plasma cells”?

B‐cell depletion can improve disease in some patients with rheumatoid arthritis or multiple sclerosis, indicating the pathogenic contribution of B cells to autoimmunity. However, studies in mice have demonstrated that B cells have immunosuppressive functions as well, with IL‐10 being a critical mediator of B‐cell‐mediated suppression. IL‐10‐secreting B cells have been shown to promote disease remission in some mouse models of autoimmune disorders. Human B cells also produce IL‐10, and evidence is accumulating that human IL‐10‐producing B cells might inhibit immunity. There is considerable interest in identifying the phenotype of B cells providing IL‐10 in a suppressive manner, which would facilitate the analysis of the molecular mechanisms controlling this B‐cell property. Here, we review current knowledge on the B‐cell subpopulations found to provide suppressive functions in mice, considering both the pathological context in which they were identified and the signals that control their induction. We discuss the phenotype of B cells that have IL‐10‐dependent regulatory activities in mice, which leads us to propose that antibody‐secreting cells are, in some cases at least, the major source of B‐cell‐derived regulatory IL‐10 in vivo. Anti‐inflammatory cytokine production by antibody‐secreting cells offers a novel mechanism for the coordination of innate and humoral immune responses.     

Lessons from helminth infections: ES‐62 highlights new interventional approaches in rheumatoid arthritis

Parasitic worms are able to survive in their mammalian host for many years due to their ability to manipulate the immune response by secreting immunomodulatory products. It is increasingly clear that, reflecting the anti‐inflammatory actions of such worm‐derived immunomodulators, there is an inverse correlation between helminth infection and autoimmune diseases in the developing world. As the decrease in helminth infections due to increased sanitation has correlated with an alarming increase in prevalence of such disorders in industrialized countries, this ‘hygiene hypothesis’ has led to the proposal that worms and their secreted products offer a novel platform for the development of safe and effective strategies for the treatment of autoimmune disorders. In this study we review the anti‐inflammatory effects of one such immunomodulator, ES‐62 on innate and adaptive immune responses and the mechanisms it exploits to afford protection in the murine collagen‐induced arthritis (CIA) model of rheumatoid arthritis (RA). As its core mechanism involves targeting of interleukin (IL)‐17 responses, which despite being pathogenic in RA are important for combating infection, we discuss how its selective targeting of IL‐17 production by T helper type 17 (Th17) and γδ T cells, while leaving that of CD49b⁺ natural killer (NK and NK T) cells intact, reflects the ability of helminths to modulate the immune system without immunocompromising the host. Exploiting helminth immunomodulatory mechanisms therefore offers the potential for safer therapies than current biologicals, such as ‘IL‐17 blockers’, that are not able to discriminate sources of IL‐17 and hence present adverse effects that limit their therapeutic potential.     

Targeted IL‐4 therapy synergizes with dexamethasone to induce a state of tolerance by promoting Treg cells and macrophages in mice with arthritis

F8‐IL‐4 is a recently developed immunocytokine that delivers IL‐4 to sites of inflammation by targeting the neovasculature. We previously reported that F8‐IL‐4, in combination with dexamethasone (DXM), provides a durable therapy in mice with collagen‐induced arthritis (CIA). Therefore, the objective of this study was to identify the mechanism by which IL‐4 and DXM combination therapy provides long‐lasting disease remission. F8‐IL‐4 alone attenuated inflammation in CIA and this was associated with increased T_H2 and decreased T_H17 cell numbers in the joints. Similarly, DXM alone had an antiinflammatory effect associated with lower T_H17 cell numbers. In both cases, these therapeutic benefits were reversed once treatment was stopped. On the other hand, combination therapy with F8‐IL‐4 plus DXM led to a synergistic increase in the percentage of regulatory T (Treg) cells and antiinflammatory macrophages in the arthritic joint and spleen as well as IL‐10 levels in serum and spleen. The net result of this was a more pronounced attenuation of inflammation and, more importantly, protection from arthritis relapse post therapy retraction. In conclusion, F8‐IL‐4 plus DXM is a durable treatment for arthritis that acts by promoting Treg cells in a synergistic manner, and by producing a sustained increase in antiinflammatory macrophages.     

Exacerbated experimental arthritis in Wiskott–Aldrich syndrome protein deficiency: Modulatory role of regulatory B cells

Patients deficient in the cytoskeletal regulator Wiskott–Aldrich syndrome protein (WASp) are predisposed to varied autoimmunity, suggesting it has an important controlling role in participating cells. IL‐10‐producing regulatory B (Breg) cells are emerging as important mediators of immunosuppressive activity. In experimental, antigen‐induced arthritis WASp‐deficient (WASp knockout [WAS KO]) mice developed exacerbated disease associated with decreased Breg cells and regulatory T (Treg) cells, but increased Th17 cells in knee‐draining LNs. Arthritic WAS KO mice showed increased serum levels of B‐cell‐activating factor, while their B cells were unresponsive in terms of B‐cell‐activating factor induced survival and IL‐10 production. Adoptive transfer of WT Breg cells ameliorated arthritis in WAS KO recipients and restored a normal balance of Treg and Th17 cells. Mice with B‐cell‐restricted WASp deficiency, however, did not develop exacerbated arthritis, despite exhibiting reduced Breg‐ and Treg‐cell numbers during active disease, and Th17 cells were not increased over equivalent WT levels. These findings support a contributory role for defective Breg cells in the development of WAS‐related autoimmunity, but demonstrate that functional competence in other regulatory populations can be compensatory. A properly regulated cytoskeleton is therefore important for normal Breg‐cell activity and complementation of defects in this lineage is likely to have important therapeutic benefits.