Phagocytosis of opsonized RBCs by isolated splenic macrophages from SHPS-1 mutant mice. Adherent splenic macrophages derived from WT (○) or homozygous SHPS-1 mutant (•) mice were assayed for their phagocytic responses in vitro with nonopsonized (left) or IgG-opsonized (right) RBCs from WT donor mice. The phagocytic index was determined after incubation of cells for the indicated times at 37°C. Data are means ± SE of values from 3 independent experiments.