Card9^−/− mice develop efficient T cell responses to mycobacterial infections. (A) Lymphocyte percentages were similar in MTB-infected Card9^−/− and WT mice at 14 and 28 d p.i. as shown by FACS analysis of CD4⁺ and CD8⁺ lung T cell populations. (B) Card9^−/− mice mounted normal lung T cell responses, as revealed by frequencies of MTB-specific PepA tetramer⁺ (GAPINSATAM) CD8⁺ T cells and IFN-γ/IL-2⁺ CD4⁺ or CD8⁺ T cells. Data are representative of two independent experiments (n = 5). Two-way ANOVA and Bonferroni method were applied for statistical analyses. (C) WT and Card9^−/− mice develop similar DTH responses 3 wk after BCG vaccination (n = 12). (D) Survival of Card9^−/− mice challenged with 200 CFUs of MTB H37Rv is significantly prolonged by BCG vaccination (n = 10). Data shown is from one experiment (C and D).