MHC-II KO recapitulated H2-Aa ^cit/cit tumor inhibition and phenotyping of H2-Aa ^cit/cit mice. (A) Tumor growth curves of B16F10 melanoma after s.c. inoculation on day 0 into the flank of mice (n = 7 or 8 per group). (B) Survival curves of mice after i.v. inoculation with B16F10 melanoma on day 0. Mice were intraperitoneally (i.p.) injected with anti-PD1 twice per week till the end of the experiment (death or euthanasia) (n = 10 per group). (C–K) CD8 T cells (C), CD4 T cells (D), B cells (E), B1 cells (F), NK cells (G), monocytes (H), neutrophils (I), red blood cells (RBC, J), and platelets (K) in H2-Aa^cit/cit mice and WT littermates. Data were collected by flow cytometric analysis with counting beads (C–I). Data were obtained using a Hemavet 950 (J and K). (L) ELISA analysis of cytokines in the peripheral blood plasma of WT and H2-Aa^cit/cit mice. Data are representative of two independent experiments (A–K). WT C57BL/6J mice from JAX (A and B) and WT littermates (C–L) were used as controls. Error bars indicate SEM (A) or SD (C–L). P values were determined by two-way ANOVA with post-hoc Tukey test (A), log-rank test (B), or Student’s t test (C–L). Each symbol represents an individual mouse (C–L). n = 4 per group (C–L). *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns, not significant.