The influence of cytomegalovirus carrier status on lymphocyte subsets and natural immunity

The influence of the cytomegalovirus (CMV) carrier status on peripheral lymphocyte subsets was studied in 70 healthy individuals. IgG-class antibodies against CMV late antigen were used as markers for the presence of CMV in those individuals. The 39 CMV-seropositive individuals had significantly higher numbers of CD3+ (P = 0.009), CD8+ (P = 0.005) and HNK1+ (P = 0.002) cells than the 31 CMV-seronegative individuals. Two-colour immunofluorescence studies revealed that the HNK1+ cells coexpressing CD4 or high density CD8 were particularly increased in the number under the influence of CMV, but not the HNK1+ cells coexpressing CD16. Since HNK1 and CD16 are markers associated with natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC), we investigated the influence of the CMV carrier status on those functions. The NK and ADCC functions of peripheral blood mononuclear cells (PBMC), HNK1+ and HNK1- cells were correlated with the percentages of CD16+ cells among those cells. Although CMV-seropositive individuals had significantly less CD16+ cells among their HNK1+ cells than CMV-seronegative individuals (mean and s.d.: 39 and 19%, versus 58 and 11%, P = 0.003), the NK and ADCC functions of the HNK1+ cells were similar in both groups. Also, the CMV carrier status did not influence significantly those functions of PBMC and HNK1- cells. We conclude that the CMV carrier status, i.e. CMV-seropositivity, is associated with a significant increase in the numbers of HNK1+ lymphocytes coexpressing T cell markers. That situation may reflect the continuing interaction between CMV and the immune system of its host.