Binding of erythrocytes to CHO cells transfected with SIRPα. (A) A fraction of erythrocytes obtained from fresh blood binds to CHO SIRPα cells, whereas no binding was observed to mock-transfected cells. Binding of erythrocytes to CHO SIRPα cells is dependent on CD47 and SIRPα. (B) The erythrocytes from fresh blood that bind to CHO SIRPα cells reside in the fraction of old erythrocytes. Data are representative of 4 experiments.