Skin-Resident Immune Cells Actively Coordinate Their Distribution With Epidermal Cells During Homeostasis

The study investigated how skin-resident immune cells, specifically Langerhans cells (LCs) and Dendritic Epidermal T cells (DETCs), coordinate their distribution with epithelial cells during homeostasis in live adult mice. It was found that LCs and DETCs maintain their positions despite the turnover of neighboring basal epithelial stem cells and explore basal epithelial cell junctions through dendritic extensions. Changes in epithelial cell density affected immune cell density, indicating that epithelial cells regulate immune tissue composition. LCs and DETCs were organized in a tiling pattern, actively maintained even when cells were removed. The GTPase Rac1 was necessary for LCs to maintain their positional stability and tiling pattern. These findings suggested that epidermal cells regulate immune cell density, and immune cells maintain a non-random distribution, optimizing the epidermis's response to environmental insults.