Organ to lymph node communication and intra-organ communication. The tissue microenvironment is critical to immunity and organ homeostasis. Macrophages shape the tissue microenvironment through their phagocytic capacity and function as secretagogues. The tissue microenvironment is also broadly shaped by the cells and molecules that enter it or exit it from other tissue spaces, blood vessels or lymphatic vessels. Many organs have two broad means of removing unwanted contents in the environment: macrophage-mediated phagocytic engulfment or lymphatic egress. The Randolph laboratory is interested in both of these means and works to understand how the clearance of cells and molecules from tissues impacts inflammation, disease states, and organ physiology. At the present time, most of our work focuses in the gut and its interaction with adjacent spaces like the peritoneum or adjacent organs like the liver and draining lymph nodes. We have a long-standing background in following the migration of immune cells like monocyte-derived cells out of organs and we continue to work in this area. We have also developed a strong interest in molecular migration out of organs, with a particular interest in the trafficking of lipoproteins like HDL.