Human SI contains four distinct Mf subsets. (A) Representative flow cytometric analysis of human SI Mfs, identifying Mf1 (purple) and Mf2 (green, top right), Mf3 (red), and Mf4 (blue, bottom right), and DCs (pink, top center) among CD45⁺HLA-DR⁺ SI mononuclear phagocytes. Arrows indicate sequential gating (see Fig. S1 A for extended gating strategy). Dot plots are representative of all subjects. (B) The proportion of SI mononuclear phagocyte subsets given as percentage of all Mfs and DCs (CD45⁺HLA-DR⁺) was determined by flow cytometry; bars indicate median values (n = 55). (C) Representative micrographs of SI Mf subsets sorted by flow cytometry and stained with Hemacolor reagent. n = 2. Bars, 5 µm. (D) Representative dot plots showing FSC-A (size), SSC-A (granularity), and autofluorescence of SI Mf subsets and DCs. Autofluorescence was measured as fluorescence excited by a 488-nm laser and collected by a 530/30 bandpass filter, where matched fluorochrome was not included. Data are representative of all subjects. (E) Representative flow cytometric staining of surface markers on PBDC, CD14⁺ PBMo (n = 3 or more; gated as in Fig. S1 B), and SI Mf subsets and DCs (n = 4 or more). Gray histograms represent FMO controls.