Loss of miR-31 attenuates alloreactive T-cell expansion and differentiation of effector T (T_eff) cells during cGVHD development. (A-B) Splenocytes (CD45.2⁺) from WT or miR-31 KO B6 donors were injected together with WT T cell–depleted (TCD) BM (CD45.1⁺) into lethally irradiated BALB/c recipients. Frequencies of CD45.2⁺ cells in gated live donor H2K^b+ CD4 or CD8 T cells and their absolute numbers are shown in recipient spleens (A) and thymuses (B) on day 50. (C-F) In separate experiments, splenocytes and TCD BM cells from WT or miR-31 KO B6 mice were injected into lethally irradiated BALB/c mice. On day 50 to 60, representative flow figures of CXCR5⁺PD-1^hi cells gated on live donor H2K^b+CD4⁺ cells (upper), germinal center (GC) B cells (Fas⁺GL7⁺) gated on H2K^b+B220⁺ cells, and frequency of CXCR5⁺PD-1^hi cells in donor H2K^b+CD4⁺ cells and their numbers are shown (C). Percentages of follicular Treg (Tfr) (Foxp3⁺) and Tfh (Foxp3⁻) cells in gated H2K^b+ CD4⁺ CXCR5⁺ PD-1^hi cells (D) and percentages of GC B cells in live H2K^b+ B cells and CD138⁺B220⁻ plasma cells in live H2K^b+ cells (E) and their absolute numbers are displayed. Representative flow figures and bar graphs showing the frequencies and numbers of interferon-γ–positive (IFN-γ⁺), interleukin-17A–positive (IL-17A⁺), and tumor necrosis factor α (TNFα⁺) cells in gated live donor H2K^b+ CD4 T cells in recipient spleens are displayed (F). Data shown are from 1 representative of 3 individual experiments (n = 4-5 mice per group for each experiment). *P < .05, **P < .01, ***P < .001.