Figure 5. Resident macrophages largely co-express CD11b and CD206 in human vastus lateralis muscle.

A. Representative images showing macrophage staining: CD11b (green), CD206 (red) and DAPI (cell nuclei, blue). The majority of macrophages are positive for both CD11b and CD206; however, CD11b+/CD206- macrophages can be observed (white arrows). Scale bars = 100 µm. B. Muscle section from the vastus lateralis showing a CD11b+/CD206+ (yellow arrow) and two CD11b+/CD206- (white arrows) monocytes. Notice in the larger field of view (at right) the CD11b+/CD206- monocytes are located in a patch of blood at the edge of the muscle section, validating CD206 as a reliable marker of tissue resident macrophages in human skeletal muscle. The patch of blood can be identified by its dried, cracked appearance and high red background signal (border between blood patch and muscle fibers in the section denoted with a dashed line). The gray X is marking an area with green background signal produced by a bubble underneath the section (further outlined in Figure S1). Scale bars = 50 µm. C. Bar graph quantification showing the number of total macrophages (all CD11b+) and CD11b+/CD206+ macrophages per 100 skeletal muscle fibers. Sixty-five muscle biopsies from the vastus lateralis were analyzed. Each dot represents macrophage counts from a single subject/section with overlap between Total CD11b+ and CD11b+/CD206+ groups, illustrating that the majority of macrophages (Total CD11b+) also express CD206 (CD11b+/CD206+). In skeletal muscle samples approximately 82% of the total macrophage population co-express CD11b and CD206.