CD8+ effector T cell subsets identified thus far include Tc1, Tc2, Tc9, Tc17, follicular cytotoxic T (Tfc), follicular helper T (CD8+ Tfh), and regulatory T (CD8+ Treg), holds significant potential in treating tumors, viral infections, allergies, and autoimmune diseases (135, 136).The majority of effector cells undergo apoptosis with small subset persists and differentiates into memory cells. The gene discussed is CD8A; the disease is viral infectious disease.