Impaired humoral immune response in OX40−/− mice.

(A–H) Follicular T helper cell (Tfh) and germinal center responses were analyzed 8 respectively 20 days post LCMV cl13 infection in WT (black bars and lines) and OX40−/− mice (white bars and dashed lines) and compared to naïve WT mice (grey bars). (A) Number of Bcl6+CXCR5+ Tfh cells per spleen, (B) representative FACS-plots gated on CD4 T cells. (C) Number of LCMV-specific follicular helper CD4 T cells per spleen, (D) representative FACS-plots gated on CD4 T cells. (E) Number of germinal center B cells per spleen, (F) representative FACS-plots gated on B cells showing germinal center B cell populations. (G) Number of plasma cells per spleen, (H) representative FACS-plots gated on B cells showing plasma cell populations. Representative results from 1 of 2–3 independent experiments are illustrated. (I) LCMV-specific IgG antibody titers were analyzed by Elisa on days 10, 20, 50, 80 and 120 post infection (n = 4–10 per group and time point). Data are derived from a total of 7 independent experiments, 1–2 experiments per time point.