Fusion of purified macrophages isolated from WT and Mac-1−/− mice. Macrophages were isolated from the peritoneum lavage with the use of F4/80 mAb and PE selection kit, and fusion was performed. A: Representative images of WT macrophages and Mac-1−/− obtained 48 and 72 hours after the addition of IL-4. Selected MGCs are outlined. B: The number of nuclei in MGCs derived from WT and Mac-1–deficient macrophages was determined from staining with Wright dye. C: The size of MGCs is expressed as a ratio of MGC/MNC, where MNC is the surface occupied by a mononucleated macrophage. Data are expressed as means ± SD. n = 3 experiments each with 5 random fields per slide (B). **P < 0.01. Scale bar = 100 μm. mAb, monoclonal antibody; MGC, multinucleated giant cell; MNC, mononucleated cell; PE, phycoerythrin; WT, wild-type.