Double immunofluorescence showing CD16+ and CD16- macrophages in rheumatoid arthritis synovium. Synovial tissue samples from patients with rheumatoid arthritis (RA) were stained with CD68 and CD16. (a) CD68, (b) CD16, and (c) merged (a) with (b). Arrows show CD16+ cells. Original magnification, ×400. Representative results from four RA patients are shown. Scale bar = 50 μm.