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Homeostatic cytokines reciprocally modulate the emergence of prenatal effector PLZF+CD4+ T cells in humans

The development of human adaptive immunity progresses faster than previously appreciated, with the emergence of memory CD4+ T cells alongside regulatory T (Treg) cells by the second trimester of pregnancy. We previously identified a prenatal-specific subset of PLZF+ CD4+ T cells with heightened effector potential that accounted for most memory T cells in the developing intestine and accumulated in the cord blood of infants exposed to prenatal inflammatory pathologies. However, the signals that drive their tissue distribution and effector maturation are unknown. In this report, we define the transcriptional and functional heterogeneity of prenatal PLZF+ CD4+ T cells and identify compartmentalization of Th-like effector function across the small intestine (SI) and mesenteric lymph nodes (MLN). We find that IL-7, which is more abundant in the SI relative to the MLN, drives the preferential expansion of naïve PLZF+ CD4+ T cells via JAK/STAT and MEK/ERK signaling. Exposure to IL-7 induces a subset of PLZF+ CD4+ T cells to acquire a memory-phenotype and rapid effector function, identifying the human analogue of memory-phenotype CD4+ T cells. Further, IL-7 modulates the differentiation of Th1- and Th17-like PLZF+ CD4+ T cells, and thus likely contributes to the anatomic compartmentalization of prenatal CD4+ T cell effector function.