CD4+CD25+ regulatory T cells control the magnitude ofT-dependent humoral immune responses to exogenous antigens

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Abstract
CD4+CD25+ T reg cells are critical for peripheral tolerance and prevention of autoimmunity. Here we show that CD4+CD25+ T reg also regulate the magnitude of humoral responses against a panel of T-dependent antigens of foreign origin during both primary and secondary immune responses. Depletion of CD4+CD25+ T cells leads to increased antigen-specific antibody production and affinity maturation but does not affect T-independent B cell responses, suggesting that CD4+CD25+ T reg exert a feedback mechanism on non-self antigen-specific antibody secretion by dampening the T cell help for B cell activation. Moreover, we show that CD4+CD25+ T reg also suppress in vitro B cell immunoglobulin production by inhibiting CD4+CD25– T cell help delivery, and that blockade of TGF-β activity abolishes this suppression.