FIGURE 3.

AL008 enhances the phagocytosis of tumor cells by macrophages. (A) FACS plots showing the gating strategy for measuring phagocytosis of CFSE⁺ Raji cells and CD14-allophycocyanin⁺ macrophages. CFSE⁺ Raji cells were run in the upper left quadrant (green), and CD14-allophycocyanin⁺ macrophages were run in the lower right quadrant (blue). Phagocytosis is shown in the upper right quadrant. (B) AL008 increased Ab-dependent cellular phagocytosis (ADCP) of anti-CD20 opsonized Raji B cells (right) and induced phagocytosis of Raji cells in the absence of an opsonization agent (left). Human monocyte-derived macrophages were treated with isotype control, AL008, or SIRPα-blocking Abs and cocultured with fluorescently labeled tumor cells. Raji cells were opsonized with anti-CD20 Ab as indicated. ADCP of Raji cells was measured by flow cytometry gating on the percentage of CD14⁺/CFSE⁺ macrophages. (C) AL008 promotes the phagocytosis of solid tumor and lymphoma cell lines by macrophages in the absence of opsonizing antitumor Abs. Macrophages were treated as previously described and cocultured with CFSE-labeled tumor cell lines. Phagocytosis of tumor cells was measured by flow cytometry gating on the percentage of CD14⁺/CFSE⁺ macrophages. Results were normalized to the isotype-treated cells. Each symbol represents macrophages from a different human donor. Paired Student t tests were performed. *p < 0.05, **p < 0.01, ***p < 0.001.