Fig. 3: Trim37 promotes T_FH cell differentiation in a T-cell-intrinsic manner.

a Sorting of CXCR5^–PD1^– non-T_FH cells and CXCR5⁺PD1⁺ T_FH cells from lung-draining lymph nodes and spleens in the C57BL/6 mice infected with PR8 influenza virus. b Cxcr5, Bcl6, and Trim37 mRNA expressions in non-T_FH cells and T_FH cells were measured by RT-PCR. c Schematic design of the Trim37^3×Flag mice. d CXCR5^–PD1^- non-T_FH cells and CXCR5⁺PD1⁺ T_FH cells were sorted from lung-draining lymph nodes and spleens in the Trim37^3×Flag mice infected with PR8 influenza virus. Flag, Bcl6, and β-actin protein expression was measured by Western blotting. e, f FIN_major bone marrow chimeric mice were infected intranasally with PR8 H1N1 influenza virus (0.5 LD₅₀) and sacrificed on day 12 after infection. Representative flow cytometry plots showing the frequency of CD45.1⁺ (WT, n = 4) or CD45.2⁺ (FIN_major, n = 4) CXCR5⁺ PD1⁺ T_FH cells (e) and CXCR5⁺ GL7⁺ GC-T_FH cells (f) as a percentage of CD4⁺ T cells in the spleens. g–j Flow cytometry analysis of lymphocytes from WT (n = 3) and Trim37^cko (n = 4) mice at day 10 after infection of PR8 H1N1 influenza virus (0.5 LD₅₀). g, h The frequency and quantification of CXCR5⁺ PD1⁺ (g) and CXCR5⁺Bcl6⁺ (h) T_FH cells as a percentage of CD4⁺ T cells in the draining lymph nodes. i, j The frequency and quantification of Fas⁺PNA⁺ GC B (i) cells and IgD^loCD138^hi plasma cells (j) as a percentage of B220⁺ B cells in the draining lymph nodes. Data are representative of at least three independent experiments, and were analyzed by two-tailed unpaired Student’s t-test (e–g, j), or two-way ANOVA (b). Data are mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ns, not significant.