CD8A and carcinoma: Although loss of HLA class I may benefit to carcinoma resistance to CD8+ CTL as discussed above, it could increase the susceptibility to cytotoxicity of natural killer (NK) cells [35] because HLA class I is a ligand for inhibitory receptor family, killer cell immunoglobulin-like receptor (KIR) of NK cells [36], Thus, loss of HLA class I expression could favor the escape of antigen-dependent cytotoxicity of CD8+ CTL, but at the same time carcinoma cells may become a target of NK cell cytotoxicity.