UCLA

Exposure to male antigens has been shown to induce an immune response in women. This response allows for recognition of paternal antigens, and development of maternal immune tolerance for a potential fetus. Prior exposure to a partner’s antigens has been shown to decrease risk of pregnancy complications. Humans did not evolve to exclusively have one sexual partner throughout a lifetime. We hypothesize that female physiology may have acquired an adaptation to prevent chronic inflammation, whereby exposure to a wider variety of paternal antigens could lead to the development of protective immune tolerance. In a cohort of pregnant mothers in California we collected peripheral blood, measured T-regs by flow cytometry and measured cytokines by multiplex assay. Using multiple linear regression controlling for gestational age, maternal age, and parity, we found consistent with our hypothesis, that women with more cumulative sexual partners exhibited lower levels of pro-inflammatory cytokines (IL-6 b= -0.02, p= 0.07) and a less pro-inflammatory cytokine balance (IL-6 to IL-10 ratio b= -0.052, p= 0.026). Unexpectedly, we also found that more partners were associated with lower T-reg levels (T-regs b= -1.94, p= 0.045), which could indicate that the physiological pathway toii decrease inflammation may occur via a mechanism other than T-regs. Since heightened inflammation increases risk of pregnancy complications, these findings contribute to our understanding of how life history influences reproductive health and pregnancy outcomes, and imply a possible adaptation for mitigating inflammation to optimize reproductive fitness.