Product IV-opsonized erythrocytes are phagocytosed by LPS-stimulated M-CSF–cultured monocyte-derived macrophages in an FcγRIIa-dependent manner. (A) Phagocytosis of product IV and product V-opsonized O and A erythrocytes by monocyte-derived macrophages cultured with M-CSF (left) and GM-CSF (right). The percentage of positive macrophages is shown, corrected for unopsonized erythrocytes (n = 16-25 monocyte donors of n = 8-14 independent experiments). (B) Phagocytosis of product IV– and product V–opsonized erythrocytes by unstimulated and LPS-stimulated (2 ng/mL for 60 minutes) monocyte-derived macrophages, cultured in the presence of M-CSF (left) and GM-CSF (right). The percentage of positive macrophages, corrected for unopsonized erythrocytes, is shown. Data represent means and standard error of the mean (n = 6-12 monocyte donors of n = 3-6 independent experiments). (C) Phagocytosis of product IV– and product V–opsonized erythrocytes by unstimulated and TNFα-stimulated monocyte-derived macrophages, cultured in the presence of M-CSF (left) and GM-CSF (right). The percentage of positive macrophages, corrected for unopsonized erythrocytes, is shown. Data represent means and standard error of the mean (n = 6-7). (D) Phagocytosis of product IV–opsonized erythrocytes positive for the A blood group by LPS-stimulated monocyte-derived macrophages cultured in the presence of M-CSF. FcγRII and FcγRIII were blocked by F(ab′)2 fragments. The phagocytosis of product IV–opsonized erythrocytes by unblocked macrophages stimulated with LPS was set as 100%. Data represent means and standard error of the mean (n = 4).