CD8A and viral infectious disease: Two major subsets of T cells participate in the immune response to viral infection in different ways: activated CD8+ T cells directly kill infected cells, while subpopulations of CD4+ T cells produce signalling molecules that regulate myeloid cell behaviour, drive, and support CD8 response and the formation of long-term CD8 memory, and participate in the selection and affinity maturation of antigen-specific B cells, ultimately leading to the generation of neutralizing antibodies.