Difference in absolute lymphocyte count among male and female heart transplant recipients

The impact of sex on immune composition in the setting of solid organ transplantation is unknown. Immunocompetent men and women have quantitative differences in multiple markers of immunity, including lymphocyte subsets. Lymphocytes are of particular interest given the routine use of medications targeted at cell-mediated immunity. The objective of this retrospective cohort study was to compare absolute lymphocyte count (ALC) measurements of male and female heart recipients immediately before, and 1 month after, transplantation. Data was collected on 375 adult recipients (104 female and 271 male) from 2000 to 2018 at a single center. Mean ALC was compared using Student's t-test. Women had higher mean ALC both at baseline (female 1.6 × 10³ cells/μl vs. male 1.3 × 10³ cells/μl; P < .001) and at 1 month post-transplantation (mean 1.2 × 10³ cells/μl vs. .8 × 10³ cells/μl; P < .001). This finding could have important implications for sex-based differences in predisposition to rejection or response to infection or vaccination.