Background Production of antinuclear autoantibodies (ANAs) is one of the major characteristics of the systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), but the mechanisms of their production are not known. Past studies showed athymic nude BALB/c mice developed spontaneous ANAs and lupus-like autoimmunity, and lymphopenic transfer model mice, in which CD4+CD25– cells were transferred into nude mice, produced various autoantibodies including ANAs and anti-parietal cells antibody, and organ specific autoimmune diseases.
Objectives Using the lymphopenic transfer model mice, we investigated the mechanisms of the ANA production, in terms of the differentiation of transferred T cells into follicular helper T (TFH) cells via lymphopenia-induced homeostatic proliferation (LIP). Moreover, by depleting intestinal microbiota by antibiotics administration, we elucidated the role of intestinal microbiota in this system.
Methods CD4+CD25– T cells, CD4+CD25+ T cells or whole CD4+ T cells from wild-type BALB/c mice were adoptively injected into athymic BALB/c nude mice, with or without depleting recipient mice of their intestinal microbiota by orally administering broad-spectrum antibiotics in drinking water. Immunoprecipitation, immunofluorescent staining, and ELISA were performed to detect ANAs and anti-parietal cells antibody. Flowcytometry and immunostaining were performed to detect germinal center formation, and differentiation of transferred T cells.
Results The lymphopenic mouse transfer model induced gastritis, colitis and sialoadenitis. High titer IgG-type ANAs were produced early and at high rates. Clinically important autoantibodies in SLE, such as anti- double strand-DNA, Sm, U1-RNP antibodies, were also detected by ELISA. Class switching and ANA production were enhanced when CD4+CD25+ regulatory T cells-depleted CD4+ T cells were transferred into. We identified IL-21-producing PD-1+ TFH cells which developed from CD4+CD25– conventional T cells during LIP and drove germinal center reactions with aberrant B cell responses. Depletion of intestinal microbiota resulted in significant reduction of both spontaneously occurring ANAs in nude mice and enhanced ANAs in lymphopenic transfer model. LIP and differentiation into TFH cells of transferred conventional T cells were also substantially impaired by microbiota depletion.
Conclusions This study reveals that ANA production by nude mice is enhanced by LIP-TFH cells. The novel insight that intestinal microbiota plays a critical role in producing both systemic and organ-specific antibodies would help us to understand the immunopathogenesis of systemic autoimmune diseases. Moreover, the further investigation into the crosstalk between intestinal microbiota and the innate and adaptive immune systems may lead to a new therapeutic approach to systemic autoimmune diseases.
Disclosure of Interest : None declared