A fingerprint left by cytomegalovirus infection in the human T cell compartment

Latent infection with human cytomegalovirus (HCMV) is accompanied by a strong increase in the number of resting, effector-type CD4+ and CD8+ T cells with constitutive cytolytic activity in the circulation. Longitudinal studies in kidney transplant recipients revealed that effector cells emerge early after the initial viral burst and acquire their stable phenotype in the months following primary infection. Although it is yet unsettled whether these cells are all specific for CMV encoded or induced antigens, it has become clear that T cell responses to CMV are among the broadest and strongest analyzed so far. We will here summarize the qualities of the effector-type cells found in HCMV carriers and discuss their possible role in CMV-associated pathologies.