CD8A and viral infectious disease: In humans, this is believed to be the result of instabilities in homeostatic maintenance (Czesnikiewicz-Guzik et al., 2008), and the clonal expansion of specific memory CD8+ T cells due to antigenic stimulation by persistent viral infection, such as with cytomegalovirus (CMV) (Olsson et al., 2000, Pawelec et al., 2005).