Dynamics of lymphoid-mammary epithelial cell interaction during pregnancy and lactation

Abstract Breast milk has been shown to play a key role in the transfer of immunity from mother to offspring. Antibodies and lymphoid cells can be passed through breast milk and impact offspring immunity. However, the role of these lymphoid cells in lactation and in the control of offspring immunity remains unclear. We observed that the lymphoid cells present in the breast milk are distinct from those found in the blood. Compared to the blood, breast milk T cells are enriched in a T-bet+ unconventional population. Imaging analysis revealed that these T-bet+ cells gradually accumulate in the mammary gland during pregnancy and are specifically localized around and inside the mammary epithelium. We will utilize confocal and intravital imaging of the mammary gland in virgin, pregnant, and lactating mice to characterize the dynamics of this mammary-associated T-bet+ population throughout pregnancy and lactation. Understanding the dynamics of T-bet+ cells and their anatomical localization within the mammary gland will help us decode how these cells impact the remodeling of the mammary epithelium during pregnancy and lactation. We propose that the remodeling of the mammary gland imparted by the immune system can also influence the transfer of immunity from mother to offspring, thereby affecting the development of offspring immunity. This work was supported in part by intramural funds of NIAID, NIH.