Red pulp macrophages phagocytose IgG-opsonized erythrocytes. (A) Sorted red pulp macrophages phagocytose erythrocytes opsonized with human anti-RhD antibodies, but do not phagocytose unopsonized erythrocytes. Individual values are shown for n = 10 experiments. Serum treated zymosan (STZ) serves as a positive control indicating phagocytic capacity of these cells (n = 3). (B) Phagocytosis of anti-RhD opsonized erythrocytes by red pulp macrophages can be inhibited by F(ab′)2 fragment against specific FcγRs. Isotype control, n = 9; α-FcγRI; n = 3; α-FcγRII, n = 10; α-FcγRIII, n = 10; α-FcγRII+III, n = 9. Data are normalized against phagocytosis by unblocked macrophages. (C) Phagocytosis of anti-RhD opsonized erythrocytes by red pulp macrophages can be inhibited by IVIg in a concentration-dependent manner. n = 4 for each concentration. (D) Comparison of inhibition by IVIg in various cell types. Red pulp macrophages, n = 4; spleen monocytes, n = 3, M-CSF Mφ, n = ≥22; M-CSF, n = 26. Data in panels B-D are normalized against phagocytosis by unblocked macrophages. Mean ± SEM are shown for each group throughout this figure.
