Decoding mucosal immunity: A unique natural killer cell profile in vaginal tissue.

Abstract

Abstract Mucosal immunity in the vaginal tract (VT) remains poorly characterized despite its critical role in protecting from sexually transmitted infections. NK cells, critical for resolving infections, are found in the VT in significant numbers yet it is unknown how the immune system in the VT differs from that in circulation. To address this important question, vaginal tissue and autologous blood were collected from healthy donors and NK cells were profiled using high-parameter flow cytometry (n=10) and scRNA-seq (n=4) to define differences between NK cells from blood and tissue. The scRNA-seq data revealed a unique gene signature in tissue NK cells with a downregulation in genes related to cytotoxicity. We confirmed this data utilizing a 28-color flow cytometry panel. The frequency of markers expressed on blood and tissue NK cells were analyzed using a paired t-test. We found that NK cells in the VT express increased tissue residency markers CD69 and CD103 (p=0.0001, p=0.0009) when compared to NK cells from the blood. The NK cells from the VT displayed a decrease in maturation markers and cytotoxic molecule Granzyme B (p=0.0002). Despite the quiescent nature of NK cells in the VT, these cells produce increased levels of IFNg upon stimulation with cytokines (p=0.0021). This suggests NK cells in the VT may be regulated to limit tissue damage but are poised to robustly respond to inflammatory stimuli. In sum, I demonstrate how NK cells are phenotypically unique in mucosal tissue.