FIGURE 2.

SIRP-1 and SIRP-2 Abs induce single-agent phagocytosis of a range of cancer cell lines. (A–C) SIRP-1 and SIRP-2 induced human moMΦs to phagocytose a panel of hematopoietic and solid tumor cell lines. CFSE-labeled (A, C, and D–F) or pHrodo Red–labeled (B) target cells were added to moMΦs and phagocytosis measured as the percentage of moMΦs that had engulfed target cells (CFSE⁺ or pHrodo⁺) of the total macrophage population. Single-agent phagocytosis of Jurkat T-ALL cells with SIRP-1 (D) and SIRP-2 used at 10 μg/ml (E) is seen in human moMΦs of all three most common allelic groups of SIRPα. The crosses in (A)–(D) indicate mIgG1 control at 10 μg/ml. (F) SIRP-1 and SIRP-2 did not induce moMΦ phagocytosis of autologous PBMCs in contrast to Jurkat T-ALL cells. All panels show mean ± SEM; a representative minimum n = 2 is shown.