CD8A and cancer: Cancer antigen-specified CTL activation causes identification and apoptosis of antigen-presenting cells (APCs) through production of inflammatory cytokine and cytotoxic proteins such as perforins and granzyme B. CD8+ DCs activate antigen-specific CTLs in mice when antigens are presented on major histocompatibility complex (MHC) class I, which interacts with TCRs and CD8 on T cells [134,135].