THP-1 derived macrophage phagocytosis of apoptotic Jurkat cells. A. Apoptosis induction was confirmed by the detection of percentage of Annexin V and 7-AAD staining by flow cytometric assessment. More than 50% cells were Annexin V +7-AAD-(early apoptotic cells) and less than 5% cells were Annexin V +7-AAD+ (late apoptotic and necrotic cells) after ultraviolet B irradiation. This analysis was repeated prior to each phagocytosis assay. One representative image is shown. B. Flow cytometry based phagocytosis assay. To discriminate between binding and internalization of apoptotic Jurkat cells, CD3 staining of CFSE+ macrophages was performed. Macrophages that had ingested apoptotic Jurkat cells were CD3- (upper left quadrant), while macrophages with Jurkat cells bound to their surface were CD3+ (upper right quadrant). Macrophages were pretreated with IgG from SLE patients or healthy controls before being incubated with apoptotic cells, as described in Materials and Methods. Representative flow cytometry images for phagocytosis by macrophages pretreated with IgG from control (left panel) and SLE patients with anti-class A scavenger receptor antibodies (right panel) are shown.