CD4 and AIDS: In a case-control study of CMV-seropositive individuals with AIDS and very low CD4+ T cells, we showed that the risk of CMV end-organ disease was independently associated with high proportions of CMV-specific GrB-secreting PBMC (ELISPOT) and high proportion of CMV-specific CD8+CD107a+ expanded form PBMC [22], supporting the notion that CMV-specific CD8+ Treg importantly contribute to the high morbidity and poor outcome of CMV-infected hosts with AIDS.