IL-10-producing regulatory B cells restrain the T follicular helper cell response in primary Sjögren’s syndrome

Increased numbers of T follicular helper(Tfh)cells have been implicated in the development of autoimmune diseases including primary Sjögren’s syndrome(pSS),but how the Tfh cell response is regulated during autoimmune pathogenesis remains largely unclear.Here,we first found negative correlations between IL-10^(+)regulatory B(Breg)cell numbers and Tfh cell responses and disease activity in patients with pSS and mice with experimental Sjögren’s syndrome(ESS).Moreover,we detected high expression of IL-10 receptor on Tfh cells and their precursors in both humans and mice.In culture,IL-10 suppressed human and murine Tfh cell differentiation by promoting STAT5 phosphorylation.By using an adoptive transfer approach and two-photon live imaging,we found significantly increased numbers of Tfh cells with enhanced T cell homing into B cell follicles in the draining cervical lymph nodes of RAG-2−/−mice transferred with IL-10-deficient B cells during ESS development compared with those of RAG-2−/−mice transferred with wild-type B cells.In ESS mice,CD19^(+)CD1d^(hi)CD5^(+)Breg cells with decreased IL-10 production exhibited severely impaired suppressive effects on T cell proliferation.Consistently,CD19^(+)CD24^(+)CD38^(hi) Breg cells from pSS patients showed significantly reduced IL-10 production with defective inhibitory function in the suppression of autologous Tfh cell expansion.Furthermore,the adoptive transfer of IL-10-producing Breg cells markedly suppressed the Tfh cell response and ameliorated ESS progression in ESS mice.Together,these findings demonstrate a critical role for IL-10-producing Breg cells in restraining the effector Tfh cell response during pSS development.

IL-17 sustains the plasma cell response via p38-mediated Bcl-xL RNA stability in lupus pathogenesis

Recent studies have demonstrated a central role for plasma cells in the development of autoimmune diseases,such as systemic lupus erythematosus(SLE).Currently,both the phenotypic features and functional regulation of autoreactive plasma cells during SLE pathogenesis remain largely unclear.In this study,we first found that a major subset of IL-17 receptor-expressing plasma cells potently produced anti-dsDNA IgG upon IL-17A(IL-17)stimulation in SLE patients and lupus mice.Using a humanized lupus mouse model,we showed that the transfer of Th17 cell-depleted PBMCs from lupus patients resulted in a significantly reduced plasma cell response and attenuated renal damage in recipient mice compared to the transfer of total SLE PBMCs.Moreover,long-term BrdU incorporation in lupus mice detected highly enriched long-lived BrdU+subsets among IL-17 receptor-expressing plasma cells.Lupus mice deficient in IL-17 or IL-17 receptor C(IL-17RC)exhibited a diminished plasma cell response and reduced autoantibody production with attenuated renal damage,while the adoptive transfer of Th17 cells triggered the plasma cell response and renal damage in IL-17-deficient lupus mice.In reconstituted chimeric mice,IL-17RC deficiency resulted in severely impaired plasma cell generation but showed no obvious effect on germinal center B cells.Further mechanistic studies revealed that IL-17 significantly promoted plasma cell survival via p38-mediated Bcl-xL transcript stabilization.Together,our findings identified a novel function of IL-17 in enhancing plasma cell survival for autoantibody production in lupus pathogenesis,which may provide new therapeutic strategies for the treatment of SLE.