The menstrual cycle regulates migratory CD4 T-cell surveillance in the female reproductive tract via CCR5 signaling

Despite their importance for immunity against sexually transmitted infections, the composition of female reproductive tract (FRT) memory T-cell populations in response to changes within the local tissue environment under the regulation of the menstrual cycle remains poorly defined. Here, we show that in humans and pig-tailed macaques, the cycle determines distinct clusters of differentiation 4 T-cell surveillance behaviors by subsets corresponding to migratory memory (T_MM) and resident memory T cells. T_MM displays tissue-itinerant trafficking characteristics, restricted distribution within the FRT microenvironment, and distinct effector responses to infection. Gene pathway analysis by RNA sequencing identified T_MM-specific enrichment of genes involved in hormonal regulation and inflammatory responses. FRT T-cell subset fluctuations were discovered that synchronized to cycle-driven CCR5 signaling. Notably, oral administration of a CCR5 antagonist drug blocked T_MM trafficking. Taken together, this study provides novel insights into the dynamic nature of FRT memory CD4 T cells and identifies the menstrual cycle as a key regulator of immune surveillance at the site of STI pathogen exposure.