SIRPA and neoplasm: Based on the findings that ferumoxytol NPs (an FDA-approved iron supplement) could be phagocytosed by TAMs and detected by MR imaging in mouse models and patients, using CD47 mAbs to block the CD47–SIRPα interaction induced phagocytosis of both NPs and tumor cells, resulting in dramatically improved r2 relaxivities and increased numbers of M1 macrophages [86].