Expression of CD47 (integrin-associated protein) decreases on red blood cells during storage

In light of recent studies that demonstrate that CD47 antigen is an important "self-recognition" marker involved in protecting circulating red blood cells (RBCs) from phagocytosis by macrophages, the aim of the present study was to investigate whether CD47 expression on RBCs is altered during storage. Red cell concentrates (RCCs) were prepared and stored at 4 degrees C and samples were collected on days 1, 14, 28 and 42 post donation. RBCs were labelled with anti-CD47 antibody and analysed by flow cytometry. A small but significant and progressive decrease in CD47 antigen expression was observed in non-irradiated and irradiated RBCs stored for 14 days onwards. CD47 was also detected in increasing quantities in supernatant from RCCs after 14 days of storage. It is proposed that loss of CD47 during storage, in addition to other biophysical changes, may target many transfused RBCs for clearance from the transfusion recipient's circulation.