The microRNA cluster miR-17~92 promotes TFH cell differentiation and represses subset-inappropriate gene expression

Follicular helper T cells (TFH cells) are the prototypic helper T cell subset specialized to enable B cells to form germinal centers (GCs) and produce high-affinity antibodies. We found that expression of microRNAs (miRNAs) by T cells was essential for TFH cell differentiation. More specifically, we show that after immunization of mice with protein, the miRNA cluster miR-17~92 was critical for robust differentiation and function of TFH cells in a cell-intrinsic manner that occurred regardless of changes in proliferation. In a viral infection model, miR-17~92 restrained the expression of genes ‘inappropriate’ to the TFH cell subset, including the direct miR-17~92 target Rora. Removal of one Rora allele partially ‘rescued’ the inappropriate gene signature in miR-17~92-deficient TFH cells. Our results identify the miR-17~92 cluster as a critical regulator of T cell–dependent antibody responses, TFH cell differentiation and the fidelity of the TFH cell gene-expression program. Gene expression analysis of control versus miR-17~92 knockout (KO) LCMV-specific SMARTA TFH cells 5.5 days after viral infection.