Figure 2. GM-CSF regulates MFG-E8–mediated uptake of apoptotic cells.

(A) Purified macrophages were exposed to apoptotic cells overnight, and MFG-E8 expression was determined by flow cytometry. Numbers refer to the percentage of cells within an indicated gate. (B) Purified splenic dendritic cells or Flt3-L–derived bone marrow dendritic cells were exposed to apoptotic cells overnight and stained for MFG-E8. (C) Peritoneal macrophages were engineered to express MFG-E8, the RGE mutant, or GFP and were evaluated for the phagocytosis of labeled apoptotic thymocytes. (D) Transduced peritoneal macrophages (4 mice per group) were exposed to apoptotic thymocytes, and culture supernatants were analyzed by ELISA. (E) Transduced peritoneal macrophages were exposed to apoptotic thymocytes and then cocultured with wild-type Balb/c splenocytes with (open symbols) or without (filled symbols) neutralizing antibodies to TGF-β. Proliferation was determined by ³H-thymidine uptake. Results are representative of 2 to 4 independent experiments.