In these patients, HCMV CD4+ and CD8+ T lymphocyte responses have been shown to be critical for the control of HCMV infection, and the reconstitution of these responses following successful anti-retroviral therapy, or in the post-transplant period, is associated with a decreased incidence of clinically apparent HCMV infections, as well as improved rates of overall mortality in these patients [51,62]. Here, CD4 is linked to cytomegalovirus infection.