Macrophages play key roles in tissue regeneration and inflammation at steady-state, two processes that are essential to maintain tissue homeostasis and, if dis-regulated, can lead to pathology. We have recently discovered a peculiar population of macrophages in the distal colon that is needed to locally maintain the survival of epithelial cells in homeostasis. These macrophages are localized in the stroma, but insert “balloon-like protrusions (BLPs)” through the basement membrane in between epithelial cells. BLPs sample the fluids that are absorbed through the epithelium and instruct epithelial cells to stop absorption if fluids are overloaded with fungal toxins. We here propose a project aiming to identify the key players involved in the tripartite interaction between macrophages, epithelial cells and fungi (Aim 1), unraveling the underlying molecular and cellular mechanisms (Aim 2) and evaluating whether and how failure in this “ménage à trois” can lead to colon pathology (Aim 3).