Monitoring of lymphocyte subsets in regular blood donors

Background and Objectives To assess the effects of long‐term regular leukocyte‐reduced platelet (PLT) apheresis on lymphocyte subsets in volunteer donors. Materials and Methods We enrolled 178 participants, including Amicus‐using donors (Group A, n = 55), Trima‐using donors (Group T, n = 64), and first‐time donor controls ( n = 59). Apheresis donors completed ≥8 PLT collections within 1 year on one fixed separator. Lymphocyte‐subset measurements were performed on pre‐donation screening samples. Results After age/sex adjustment, both apheresis groups exhibited significantly lower absolute counts and percentages of natural killer (NK) cells versus controls ( p < 0.05), while CD3 + , CD4 + , CD8 + T cells, and B lymphocytes were similar among groups. Several T‐cell markers showed nominal downward trends with higher lifetime donations (raw p < 0.05), yet no associations persisted after correcting for false discovery rate (FDR). Neither lifetime nor 1‐year donation counts correlated with lymphocyte or routine hematological parameters; overall lymphocyte‐subset profiles did not differ between Group A and Group T. Subgroup analysis revealed reduced NK cell counts only in the high‐donation stratum (≥100 donations) of Group A and the low‐donation stratum (<40 donations) of Group T. Conclusion Long‐term leukocyte‐reduced PLT apheresis is associated with decreased circulating NK cells. Multiple‐testing correction provided no evidence for progressive lymphocyte decline with cumulative donations. One‐year donation frequency had no impact on lymphocyte subsets. With plasma rinseback activated for all Trima procedures, lymphocyte profiles were comparable between devices. Routine hematological parameters remained stable in long‐term apheresis donors.