Human serous cavity macrophages and dendritic cells possess counterparts in the mouse with a distinct distribution between species.

In mouse peritoneal and other serous cavities, the transcription factor GATA6 drives the identity of the major cavity resident population of macrophages, with a smaller subset of cavity-resident macrophages dependent on the transcription factor IRF4. Here we showed that GATA6(+) macrophages in the human peritoneum were rare, regardless of age. Instead, more human peritoneal macrophages aligned with mouse CD206(+) LYVE1(+) cavity macrophages that represent a differentiation stage just preceding expression of GATA6. A low abundance of CD206(+) macrophages was retained in C57BL/6J mice fed a high-fat diet and in wild-captured mice, suggesting that differences between serous cavity-resident macrophages in humans and mice were not environmental. IRF4-dependent mouse serous cavity macrophages aligned closely with human CD1c(+)CD14(+)CD64(+) peritoneal cells, which, in turn, resembled human peritoneal CD1c(+)CD14(-)CD64(-) cDC2. Thus, major populations of serous cavity-resident mononuclear phagocytes in humans and mice shared common features, but the proportions of different macrophage differentiation stages greatly differ between the two species, and dendritic cell (DC2)-like cells were especially prominent in humans.