SAP-independent inhibitory SFR signaling leads to severe defects in humoral immunity in SAP-deficient mice. (A) Representative flow cytometry plots and percentages of splenic and LN GC T_FH cells (CD4⁺CD19⁻PD1^hiCXCR5^hi) or GC B cells (CD19⁺Fas^hiGL7^hi) from the indicated mice 7 d after SRBC immunization. Data represent the mean ± SEM of 8–15 mice per group. **, P < 0.01; ***, P < 0.001. (B) Representative flow cytometry plots (left) and percentages (right) of splenic GC B cells (CD19⁺Fas^hiGL7^hi), plasma cells (CD19⁺IgD^loCD138^hi), and GC T_FH cells (CD4⁺CD19⁻PD1^hiCXCR5^hi) from the indicated mice 9 d after OVA immunization. Data represent the mean ± SEM of 5–25 mice per group. *, P < 0.05; **, P < 0.01; ***, P < 0.001.