Fig 1: mTOR complex 2 is critical for follicular helper CD4+ T (TFH) differentiation during acute viral infection. (A–D) Cd4-CreRictorfl/fl mice (Rictor−/−) and littermates Rictorfl/fl (WT) mice were infected with lymphocytic choriomeningitis virus (LCMV) Armstrong, and CD4+ T cell responses were assessed in spleen at day 8 after infection. (A) Flow cytometry of TFH (SLAMloCXCR5+) and TH1 (SLAMhiCXCR5−) cells among gp66 tetramer-positive CD4+ T (gp66+ CD4+) cells of Rictor−/− (top) and WT mice (bottom) (left), and summary of the frequency (top) and cell number (bottom) (right) (n = 8 mice per group). (B) Representative flow cytometry plots showing the expression levels of CXCR5, Bcl-6, PD-1, and ICOS on tetramer-positive TFH cells as in (A) from Rictor−/− and WT mice (top), and summary of the mean fluorescence intensity (bottom) (n = 8 mice per group). (C) Flow cytometry of bulk activated TFH (GITRloCD44hiCXCR5+) and TH1 (GITRloCD44hiCXCR5−) cells of Rictor−/− (top) and WT mice (bottom) (left), and summary of the frequency (top) and cell number (bottom) (right) (n = 8 mice per group). (D) Flow cytometry of germinal center TFH cells (Bcl6hicMafhi) among bulk activated TFH cells (GITRloCD44hiCXCR5+) of Rictor−/− (top) and WT mice (bottom) (left), and summary of the frequency (top) and cell number (bottom) (right) (n = 4–5 mice per group). (E,F) Flow cytometry of CD4+ T cell responses in the spleen of KO versus WT bone marrow (BM) chimeras at 8 days after LCMV infection. KO BM chimeras were generated with a mixture of BM cells from Rictor−/− (CD45.2+) and C57BL/6J (WT) (CD45.1+) mice, and WT BM chimeras were reconstituted with a mixture of BM cells from Rictorfl/fl (CD45.2+) and C57BL/6J (WT) (CD45.1+) mice. (E) Representative flow cytometry plots showing competitive contributions by CD45.2+ cells to the total CD4+, gp66+ CD4+, gp66+ TFH, and TH1 cell population in KO and WT BM chimeras (left). Comparison of the contribution of CD45.2+ cells to gp66+ CD4+ versus total CD4+, gp66+ CD4+ versus gp66+ TFH, and gp66+ CD4+ versus gp66+ TH1, respectively (right) (n = 4 mice per group). (F) Expression of CXCR5 and Bcl-6 in KO and WT BM chimeras (n = 4 mice per group). ns, not significant, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 [unpaired (A–D) or paired (E,F) two-tailed t-test]. Data are representative of four (A–D) or two (E,F) independent experiments. Error bars are SEM (A–F).