Evaluation of T-lymphocyte subsets present in semen and peripheral blood of healthy donors: a report from the heterosexual transmission study.

The purpose of this study was to accurately determine the T-lymphocyte subsets found in semen from healthy volunteers, to evaluate the impact of repeated ejaculation on the frequency or type of immune cells present in semen, and to compare subset analysis in semen to that in the peripheral blood. To accomplish this, a flow cytometric method was developed to identify and count immunophenotypically distinct cells present in semen. Fresh semen samples and peripheral blood were collected over three consecutive days from nine healthy donors. Donors had normal ejaculate volume, sperm count, sperm motility, morphology, and leukocyte count. No significant intra-donor differences were seen in these parameters over time. No significant differences were observed in the percentage of CD3+ cells, CD4+ cells, CD8+ cells, and the CD4:CD8 ratio in semen on consecutive days. However, within the CD4+ subset, when naive and memory CD4+ cells were measured, some day to day variability was suggested. No significant differences in CD3+, CD4+, CD8+, CD4/CD8 ratio, or naive and memory subsets were seen in the peripheral blood between sampling days. When semen was compared to peripheral blood some differences in immune subset values were observed, with an increase in the percentage of memory CD4+ cells in semen being the most striking. This finding may be relevant to HIV transmission, since others have shown that this cell may be preferentially infected with HIV and is the primary reservoir for virus in infected individuals.