The percentage of CD4+CD28null T cells was strongly correlated with the total CMV-specific CD4+ response (rho = 0.846, P <0.001; Fig. 1b), indicating that the size of the CD4+CD28null T-cell accumulation is a good measure of the impact of CMV infection on the CD4 compartment in this population. The gene discussed is CD4; the disease is cytomegalovirus infection.