It is well established that HCMV establishes a latent infection in CD34+ hematopoietic progenitor cells [35], and recent studies indicate that persistence is maintained, in part, through HCMV-induced generation of CD4+ T cells that secrete cIL-10 in response to HCMV antigens. This evidence concerns the gene CD34 and disease arising from reactivation of latent virus.