Macrophages present in Wallerian degeneration express SIRPα in wild-type mice. a–f Cryostat sections in which CD47 (a, c, e) and SIRPα (b, d, f) were visualized by immunofluorescence microscopy using anti-CD47 and anti-SIRPα mAbs. Sections were taken from intact sciatic nerve (a, b), sciatic nerve undergoing in vivo Wallerian degeneration for 5 days (c, d), and cultured sciatic nerve explant undergoing in vitro Wallerian degeneration for 5 days (e, f). All three tissues displayed immunoreactivity to CD47 whereas only sciatic nerve undergoing in vivo Wallerian degeneration displayed immunoreactivity to SIRPα. Bar in f: 100 μm, for a through f. g–o Three macrophages (g–i), (j–l), and (m–o) from 7 days in vivo Wallerian degenerating nerve segments were visualized by immunofluorescence microscopy using anti-SIRPα (g, j, m; red) and anti-αM/CD11b subunit of CR3 (h, k, n; green) Abs. SIRPα and CR3 combined (i, l, o). Hoechst staining visualized nuclei (blue). The three cells displayed immunoreactivity to both SIRPα and CR3. Bar in o: 5 μm, for g through o.