Cytokine and metabolite networks shape T cell residency and functionality at the term human maternal-fetal interface.

Placentation presents immune conflict between mother and fetus, yet in normal pregnancy maternal immunity against infection is maintained without expense to fetal tolerance. This is believed to result from adaptations at the maternal-fetal interface (MFI), which affect T cell programming, but the identities (i.e. memory subsets and antigenic specificities) of T cells and the signals that mediate T cell fates and functions at the MFI remain poorly understood. We found intact recruitment programs as well as proinflammatory cytokine networks that can act on maternal T cells in an antigen-independent manner. These inflammatory signals elicit T cell expression of costimulatory receptors necessary for tissue retention, which can be engaged by local macrophages. Although proinflammatory molecules elicit T cell effector functions, we show that additional cytokine (transforming growth factor β1) and metabolite (kynurenine) networks may converge to tune T cell function to those of sentinels. Together, these data demonstrate that T cells at the MFI are broadly recruited and restrained in an antigen-independent, cytokine/metabolite-dependent manner. These mechanisms provide insight into antigen-nonspecific T cell regulation, especially in tissue microenvironments in which they are enriched.