IL-10 induces a STAT3-dependent autoregulatory loop in Th2 cells that promotes Blimp-1 restriction of cell expansion via antagonism of STAT5 target genes

Blimp-1 expression in T cells extinguishes the T follicular helper cell fate and drives terminal differentiation, but also limits autoimmunity. Although various factors have been described to control Blimp-1 expression in T cells, little is known about what regulates Blimp-1 expression in Th2 cells and the molecular basis of its actions. Herein, we report that STAT3 unexpectedly played a critical role in regulating Blimp-1 in Th2 cells. Furthermore, we found that the cytokine IL-10 acted directly on Th2 cells and was necessary and sufficient to induce optimal Blimp-1 expression through STAT3. Together, Blimp-1 and STAT3 amplified IL-10 production in Th2 cells, creating a strong autoregulatory loop that enhanced Blimp-1 expression. Increased Blimp-1 in T cells antagonized STAT5-regulated cell cycle and anti-apoptotic genes to limit cell expansion. These data elucidate the signals required for Blimp-1 expression in Th2 cells and reveal an unexpected mechanism of action of IL-10 in T cells, providing insights into the molecular underpinning by which Blimp-1 constrains T cell expansion to limit autoimmunity. RNAseq of activated undifferentiated CD4 T cells with or without exogenous expression of Blimp-1.