Since 1993 the Japanese Red Cross has adopted a new additive solution for red cell concentrate (RC), MAP (mannitol-adenine-phosphate), which is a modifided SAGM solution. However, frequent macroaggregate formation in MAP-additive RC (MAP-RC) has become a problem. We investigated the mechanism of macroaggregate formation in MAP-RC and sought method to reduce the frequency of such formation. During 3-week storage at 4°C, macroaggegates were formed in 30% of the buffy coat-poor RC (BP-RC) prepared by the conventional method without MAP, but in 100% of MAP-RC.
Electron microscopic observation of the macroaggregates showed that red cells were trapped in a network structure, and enzyme treatments indicated that the network was made of DNA that leaked from granulocytes. The granulocytes stored in the MAP solution, however, formed macroaggregates only if plasma was added to the cell-suspension medium. Immunoblotting analysis indicated that fibrinogen and fibronectin were the constituents of the macroaggregate in addition to the DNA. Pre-storage filtration of MAP-RC with a leukocyte-removal filter (PALL BPF4) or preparation of BP-RC with the top & bottom system completely prevented the macroaggregate formation in the MAP-RC. These results indicated that reduction of leukocytes in MAP-RC to less than 1×108/bag is necessary to prevent macroaggregate formation.
