Chronic viral infections such as HCMV (104), human immunodeficiency virus (HIV) (105), hepatitis C virus (106), and Epstein–Barr virus (EBV) (107) infections offer some of the clearest examples of expansion of CD57+CD8+ T cells, presumably as a result of persistent antigenic stimulation, and increased proportions of CD57+CD8+ T cells have also been reported in those infected with human parvovirus (108), measles (109), pulmonary tuberculosis (92), and toxoplasmosis (93). The gene discussed is CD8A; the disease is toxoplasmosis.