NanoString gene expression analysis confirmed transcription of a core set of macrophage-related genes, including MAF, MERTK, F13A1, CD163, and CD14. Although GVHD macrophages have higher expression of monocyte antigens and a number of important functional differences, they are most closely related to CD11c+CD14+ dermal cells found in steady-state tissues and previously reported to have a transient, monocyte origin (25). Here, MAF is linked to graft versus host disease.