CHO SIRPα cells bind and phagocytose erythrocytes. (A) Phagocytosed erythrocytes were detected by intracellular glycophorin A staining in combination with a secondary goat anti–mouse Alexa-647 antibody. (B) Expression levels of different SIRPα constructs expressed in CHO cells, as detected by flow cytometry. (C) Binding of CD47 beads to CHO cells transfected with different constructs of SIRPα in the absence of serum. (D) Erythrocyte binding to CHO cells transfected with different SIRPα constructs in the absence of serum. Data are representative of 3 experiments. ns indicates not significant. **P < .01; ***P < .001.