CD44 mediates phagocytosis independently of Fcγ receptors. (A) Efficiency of phagocytosis of CD44 Ebabs or IgG_2b-coated Ebabs or IgG-opsonized erythrocytes by wild-type or CD44-deficient peritoneal macrophages. *Different from CD44-Ebabs/Cd44^+/+ (WT); P < .05, mean ± SE of 4 separate experiments. (B) Efficiency of phagocytosis of CD44 Ebabs by RAW macrophages that have been preincubated with the vehicle control or blocking CD44 antibody or non–immune isotype control antibody. *Significant differences at the P < .05 level, mean ± SE of 4 separate experiments. (C) Efficiency of phagocytosis of IgG-opsonized erythrocytes or CD44 Ebabs by RAW cells that were preincubated with increasing concentrations of Fcγ-blocking aggregated IgG. *Different from 0 μg/mL aggregated IgG/IgG-opsonized erythrocytes; P < .05; **P < .01, mean ± SE of 4 separate experiments. Phagocytosis was recorded as the phagocytic index.