(A and B) Skin cryosections from CD18^WT (A) and affected CD18^hypo mice (B) were stained with F4/80–Alexa 488 for infiltrating macrophages (green) into the skin. Cell nuclei (blue) were counterstained with DAPI. e, epidermis; d, dermis; h, hair follicle. Dotted lines indicate the border between epidermis and dermis. Original magnification, ×40; inset, ×100. (C) To quantify macrophages in the skin of affected CD18^hypo and CD18^WT mice, the positively stained cells were calculated. For all measurements, the median of macrophages counted in 12 high-power fields (HPF) is presented (n = 4). ^##P < 0.0001, Student’s t test. (D and E) Immunostaining with macrophage/monocyte-FITC (clone MOMA-2) was performed on cryosections of skin DLNs from CD18^WT (D) and affected CD18^hypo mice (E). Infiltrated macrophages (green) were found in the medullar and subcapsular sinuses, as indicated by arrows. Cell nuclei (red) were counterstained with propidium iodide (PI). Original magnification, ×20. (F and G) To quantify macrophages in the skin DLNs of CD18^WT (F) and affected CD18^hypo mice (G), skin DLN cells were labeled with MOMA-2–FITC and analyzed by flow cytometry. Dotted line, isotype control; gray histogram, MOMA-2 staining. (H) Total number of macrophages in skin DLNs of CD18^hypo and CD18^WT mice (n = 6). One representative experiment of 3 is shown. **P < 0.01, Student’s t test.