CD4 and cytomegalovirus infection: Further, a) men who had both high percentages of IFN-γ-SP CD4 T cells and low percentages of TP CD8 T cells progressed to frailty faster than other men; b) such men comprised most of those who progressed to frailty; and c) serum levels of CRP, which have been associated with CMV infection and frailty [8, 34], were correlated positively with percentages of IFN-γ-SP CD4 T cells and negatively with percentages of TP CD8 T cells.