Vitamin A mediates conversion of monocyte-derived macrophages into tissue-resident macrophages during alternative activation

It remains unclear whether activated inflammatory macrophages can adopt features of tissue-resident macrophages, or what mechanisms might mediate such a phenotypic conversion. Here we show that vitamin A is required for the phenotypic conversion of interleukin 4 (IL-4)-activated monocyte-derived F4/80(int)CD206(+)PD-L2(+)MHCII(+) macrophages into macrophages with a tissue-resident F4/80(hi)CD206(-)PD-L2(-)MHCII(-)UCP1(+) phenotype in the peritoneal cavity of mice and during the formation of liver granulomas in mice infected with Schistosoma mansoni. The phenotypic conversion of F4/80(int)CD206(+) macrophages into F4/80(hi)CD206(-) macrophages was associated with almost complete remodeling of the chromatin landscape, as well as alteration of the transcriptional profiles. Vitamin A-deficient mice infected with S. mansoni had disrupted liver granuloma architecture and increased mortality, which indicates that failure to convert macrophages from the F4/80(int)CD206(+) phenotype to F4/80(hi)CD206(-) may lead to dysregulated inflammation during helminth infection.