CD8A and infectious disease: Such non-specific protection by BCG against non-mycobacterial infections and perhaps other non-infectious disorders include induction of: (i) a heterologous TH1, TH17, and CD8+ lymphocytic response and (ii) a non-specific memory in innate immune cells (natural killer cells, monocytes, and macrophages) through epigenetic effects and metabolic rewiring in a paradigm known as “trained immunity” [33].