If the cancer mass expresses few neo-antigens, then greater numbers of Treg cells infiltrate to form a Treg-dominant tumor microenvironment; whereas, if the cancer mass expresses abundant neo-antigens, fewer Treg cells infiltrate, and more effector cells including CD8+ T cells can be primed and expand in the tumor tissues (16, 85, 86). The gene discussed is CD8A; the disease is cancer.