Defining the Functions of Entero-Mammary T cells in Lactogenesis and Maternal-Offspring Immunity - Project Summary / Abstract The entero-mammary axis, which is the interaction between the intestine and the mammary gland, is crucial for maternal protection of offspring. In changing environments, mothers must provide appropriate nutritional and immune support, but the mechanisms by which they shape milk composition and ensure immune protection for their offspring remain poorly understood. The broad, long-term goal of this application is to enhance our understanding of how entero-mammary communication improves maternal-offspring immunity. This has significant implications for maternal and offspring health, such as reduced risk of chronic diseases in both, and stronger intestinal immunity in the offspring, aligning with the NIAID's mission to improve health outcomes through research on infectious and immunologic conditions. The objective is to investigate the functions of specialized intestinal T cells, called intraepithelial lymphocytes (IELs), that are recruited to the mammary gland during lactogenesis. Our central hypothesis is that entero-mammary IELs promote maternal-offspring immunity by regulating milk-producing mammary epithelial cells and shaping milk composition. The rationale is that identifying the mechanisms by which IELs regulate milk composition could lead to strategies for enhancing maternal immunity, improving breastfeeding outcomes and boost offspring health in early life. The specific aims of this study include 1) investigating how IELs influence milk metabolites to modulate offspring health and support the recovery of mammary epithelial cells after infection or injury during lactation, 2) mapping interactions between IELs and epithelial cells, including TCR-specific entero-mammary IELs, to understand regulatory mechanisms of IELs, and 3) determining the effects of maternal influences, such as diets, infections, and reproductive hormones on entero-mammary IEL dynamics during lactation and as a result, offspring health. Several cutting- edge techniques will be employed to perform this study, including in-vivo labeling of cells followed by single cell RNAseq, spatial transcriptomics, metabolomics, TCR engineering, and spectral flow cytometry. The successful completion of these studies will establish the role of the recently identified entero-mammary IELs in lactogenesis, as well as pinpoint the mechanisms by which these cells regulate mammary epithelial cells, uncovering a novel function of IELs. This proposal is highly innovative as it explores the largely uncharted territories of the entero- mammary axis and immune cell involvement in enhancing milk composition, leading to healthy immune development in offspring. By examining how immune cells, particularly T cells, regulate lactogenesis, this research will pave the way for a burgeoning field with significant implications for maternal-offspring immunity. This study will make a substantial contribution to the fields of maternal and child health, as well as intestinal immunity, mammary immunity, and infectious disease research, by revealing the intricate interplay between immune cells and milk production during lactation.
