In support, compelling data on the anti-tumor activity of anti-CD47 mAbs (that is, B6H12.2 and Hu5F9-G4) or SIRPα-Fc construct have been reported.9, 11, 12, 19, 27 However, the Fc region of the anti-CD47 mAbs and SIRPα-Fc utilized in these studies consisted of murine IgG1 (B6H12.2) and human IgG4 (Hu5F9-G4 and SIRPα-Fc), both of which bind human and murine Fc receptors and mediate effector functions.28, 29, 30, 31 Hence, these studies did not define whether the therapeutic effect observed was due to solely blocking CD47 or to an opsonizing effect combined with CD47 blocking activity. Here, SIRPA is linked to neoplasm.