Variables affecting T-lymphocyte subsets in a volunteer blood donor population.

Inversion of the normal ratio of helper/inducer (Th) to suppressor/cytotoxic (Ts) T lymphocytes is a characteristic finding in symptomatic and presymptomatic patients with acquired immunodeficiency syndrome (AIDS). As an interim measure to prevent transmission of AIDS via blood transfusion, the Stanford Blood Center performed T-lymphocyte subset analysis as a screening procedure. In this report we present results from 8715 consecutive volunteer blood donors, aged 17-77. The mean Th:Ts ratio was 2.00 +/- 0.70 with a significant trend for increasing Th:Ts with increasing age. In all age groups, donors with antibody to cytomegalovirus (CMV) had lower Th:Ts ratios than CMV-seronegative donors. 1.9% of the donors had Th:Ts values less than or equal to 0.85 and blood from these donors was not used for clinical purposes. Compared to the overall donor population, individuals with Th:Ts less than or equal to 0.85 tended to be male, (79 vs 53%) and CMV sero-positive (71 vs 36%); a majority (83%) had a low absolute number of Th cells as well as a low Th:Ts value. Follow-up of donors with low Th:Ts values revealed that some belonged to AIDS high-risk populations, despite denials at the time of donation. One such donor was diagnosed with disseminated Kaposi's sarcoma 8 months after a markedly abnormal T-lymphocyte subset profile was noted during screening. These results suggest that T-lymphocyte subset analysis is capable of identifying at least some blood donors at risk for transmitting AIDS and also point to variable affecting T-cell subsets in apparently healthy blood donors.