A Noninvasive Method to Sample Immune Cells in the Lower Female Genital Tract Using Menstrual Discs.

T cells in the human female genital tract (FGT) are key mediators of susceptibility to and protection from infection, including HIV and other sexually transmitted infections. There is a critical need for increased understanding of the distribution and activation of T cell populations in the FGT, but current sampling methods require a healthcare provider and are expensive, limiting the ability to study these populations longitudinally. To address these challenges, we have developed a method to sample immune cells from the FGT utilizing disposable menstrual discs which are noninvasive, self-applied, and low in cost. To demonstrate reproducibility, we sampled the cervicovaginal fluid of healthy, reproductive-aged individuals using menstrual discs across 3 sequential days. Cervicovaginal fluid was processed for cervicovaginal cells, and high-parameter flow cytometry was used to characterize immune populations. We identified large numbers of live, CD45+ leukocytes, as well as distinct populations of T cells and B cells. Within the T cell compartment, activation and suppression status of T cell subsets were consistent with previous studies of the FGT utilizing current approaches, including identification of both tissue-resident and migratory populations. In addition, the T cell population structure was highly conserved across days within individuals but divergent across individuals. Our approach to sample immune cells in the FGT with menstrual discs will decrease barriers to participation and empower longitudinal sampling in future research studies.