CMV-seropositive patients have an altered CD4⁺ T-cell repertoire. (A) CD28⁻CD57⁺CD4⁺ T cells are present almost exclusively in CMV-seropositive patients. PBMC were stained with monoclonal antibodies against CD8, CD28, and CD57, and the relative expression of CD28 and CD57 was determined on the CD8⁺ T-cell populations of CMV-seropositive and seronegative patients. Significant differences in the number of CD57⁺, CD28⁻ and CD57⁺CD28⁻ populations were observed between the 2 groups. (B) The phenotype of the CD4⁺ T-cell repertoire is markedly altered in CMV-seropositive patients (n = 12) compared with an age-matched CMV-seropositive control group (n = 10). PBMC were stained with monoclonal antibodies against CD4, CD27, CD28, CD57, CD45RA, CD45RO, and CCR7, and the relative expression of each marker was determined in the CD4⁺ T-cell population. Significant differences were observed between the 2 groups.