Immunity https://doi.org/10.1016/j.immuni.2019.05.010 (2019)

Resident macrophage populations contribute to tissue-specific ‘identity’ programs and maintain tissue homeostasis. In Immunity, Buechler et al. describe the stromal-cell interactions required for macrophage residency in visceral body cavities that include the peritoneal, pleural and pericardial spaces. Large cavity-resident macrophages require expression of the transcription factor GATA-6. A subset of podoplanin-positive stromal cells that express the transcription factor Wt1, which include mesothelial cells and fibroblasts, also express RALDH enzymes that metabolize vitamin A and provide the retinoic acid cofactors required for GATA-6 expression for the large cavity macrophages. Depletion of Wt1+ stromal cells results in fewer peritoneal macrophages and disturbs peritoneal homeostasis. Thus, Wt1+ stromal cells are needed to provide retinol metabolites in trans to maintain cavity-resident macrophages.