Figure 4.

T_reg cell–specific TRAF3 regulates T_FH cell function and GC formation. (A and B) WT and Traf3^Treg-KO (KO) mice (8 wk old) were immunized i.p. with SRBCs, and the frequency of GC B cells (CD95⁺GL7⁺) among B220⁺ cells was assessed by flow cytometry. Data are presented as a representative plot (A) and mean ± SD based on five mice for each group (B). (C) Mice were immunized as in A and B, and GCs were analyzed by immunofluorescence detection of PNA⁺ cells. Graph shows average GC areas as mean ± SD based on multiple slides. Data are representative of four WT and three Traf3^Treg-KO (KO) mice. Bars, 500 µm. (D) Frequency of W33 to L mutation in the GC B cells of SRBC-immunized WT and Traf3^Treg-KO mice (10 d after immunization), determined by sequencing the cDNA clones constructed using pooled RNA from six WT and six KO mice. (E and F) WT-R26^YFP (WT) or Traf3^Treg-KOR26^YFP (KO) mice were immunized as in A, and 10 d later, the frequency of T_FH cells (CXCR5⁺PD-1⁺) among CD4⁺YFP⁻ T cells was assessed by flow cytometry. Data are presented as a representative plot (E) and mean ± SD (F) based on six mice for each group. (G) T_FH cells were sorted from the spleens of the WT and KO mice in E and F, and expression of the indicated genes was assessed by RT-PCR. Mean ± SEM is shown. Data in A–G are representative of three to four independent experiments. *, P < 0.05; and **, P < 0.01.