Our results show that, in comparison with the MHC-L group, the MHC-H group had higher PD-L1 expression, better immune response and prognosis, and higher mutation frequencies of both TP53 (ICI-cohort: 58 vs. 43%, P = 0.0014; TCGA-BLCA: 52 vs. 48%, P = 0.099) and RB1 (ICI-cohort: 22 vs. 11%, P = 0.005; TCGA-BLCA: 26 vs. 13%, P = 0.0012). The gene discussed is CD274; the disease is bladder transitional cell carcinoma.