Ovarian localization drives IL-7R-dependent CD8 coreceptor expression in peripheral double-negative T cells

The ovary is an immunologically dynamic tissue that coordinates recurrent inflammation-like remodeling while preserving local T cell tolerance, yet whether it actively instructs infiltrating lymphocyte phenotype or passively enriches pre-existing subsets has not been directly tested. To address this, we used peripheral double-negative T cells (DNTs; CD3⁺CD4^-CD8^-NK1.1^-) as a coreceptor-null system to detect tissue-imposed phenotypic change after ovarian entry. Using adoptive transfer, labeled splenic DNTs accumulated in the ovary relative to other tissue sites, and donor DNTs acquired surface CD8 expression within 4 days of ovarian localization. Dissociated ovarian cells were sufficient to drive CD8 upregulation on sorted DNTs in vitro, supporting that ovarian cellular cues can promote this response. Ovarian single-cell RNA-seq provided supportive evidence for Il7-expressing stromal subsets, and an Il7r-enriched DNT-associated lymphoid population, findings compatible with local IL-7-associated microenvironmental cues that may contribute to conditioning infiltrating T cells. Functionally, IL-7R was required for efficient CD8 upregulation after ovarian localization, and IL-7R or IL-7 deficiency shifted the endogenous ovarian DNT: CD8⁺ T cell balance. These findings support the ovary as an immune-conditioning environment in which tissue entry is associated with CD8 coreceptor induction on peripheral DNTs, and identify IL-7R signaling as a requirement for efficient induction in this setting.