Normal expression of p55 interleukin 2 receptor (CD25) by lymphocytes from former blood donors seropositive for human T lymphotropic virus.

Dysregulated expression of the p55 interleukin 2 receptor (CD25) is characteristic of adult T cell leukemia (ATL) associated with human T lymphotropic virus (HTLV) infection. In order to determine if similar changes characterize HTLV infection in the apparent absence of ATL, CD25 expression by peripheral blood lymphocytes from HTLV-seropositive former blood donors was measured using a sensitive dual-color cytofluorometric assay. When comparing the HTLV-seropositive group (N = 19) and a seronegative control group (N = 20), no significant differences were observed in either the proportions of the major lymphocyte subsets (CD3, CD4, CD8, CD19, CD16/56) coexpressing CD25 or the phenotypic distribution of CD25+ cells among these lymphocyte subsets. Similarly, the total percentages of CD3, CD4, CD8, and CD19 cell subsets were unchanged; however, the percentage of CD16/56+ cells was significantly decreased in the HTLV group and reflected a decrease in the percentage of CD16/56 cells lacking CD25. These findings indicate that HTLV infection without ATL is characterized by normal CD25 expression by lymphocytes and a decreased percentage of lymphocytes with a phenotype characteristic of natural killer cells.