Characterizing the role of ovarian hormones in regulating sex differences in baseline immune parameters 2309498

Introduction Sex differences among peripheral blood mononuclear cells (PBMCs) have been previously described in humans, including greater percentages (%) of CD4+ T cells in females (XX) and greater % of natural killer cells in males (XY). The role of the ovaries in regulating these and other sex differences is unknown. Methods We collected PBMCs from 80 age-matched participants (reported as mean ± SEM) and stratified into control females (n = 28; 41.6 ± 1.0 years), control males (n = 20; 40.4 ± 1.3 years), bilateral salpingo-oophorectomy (BSO) recipients (n = 16; 46.1 ± 2.0 years), and BSO recipients receiving hormone therapy (HT) (n = 16; 45.7 ± 1.2). BSO recipients were at least 1 year out from surgery. PBMCs were isolated to analyze subsets by single-cell mass cytometry. Serum was collected for estradiol (E2), testosterone (T), and progesterone measurements, and cytokines were quantified using the O-LINK platform. Results Three serum markers (IL-10, IL-17c, and CXCL11) showed a sex difference, with greater levels in males; no cytokine was modulated by BSO. Among CD45+ PBMCs, females had a greater % of CD3+ T cells, whereas the % of monocytes were greater in males. However, the sex difference in monocytes disappeared when accounting for T cell differences. Within CD4+ T cells, males had higher % of regulatory T cells and circulating follicular T cells, while within CD8+ T cells, they had higher percentages of PD-1+ effector and terminally differentiated subsets. No highlighted sex difference was associated with the presence of the ovaries. Further explorations identified a negative correlation of % of CD3+ T cells with T levels. Though not driving the sex differences, BSO did increase the % of naïve B cells at the expense of memory B cells, and this was reversed with HT. The % of naïve B cells negatively correlated with E2 and T levels. Conclusion The ovaries are not a major regulator of sex differences in immune subsets but do repress the generation of naïve B cells.