Laboratory Detection of Blood Groups and Provision of Red Cells

Red cells containing bound IgG undergo accelerated clearance through the spleen, where Fc receptors of the phagocyte bind to the IgG molecules, leading to phagocytosis of the red cell. Red cell agglutination occurs in two stages: first, the antibody binds to the red cell surface; then, the antibodies interact to bring the cells in approximation, and agglutination occurs. The second stage of agglutination is influenced by the distance between cells, the charge of molecules in the suspension, membrane deformability, membrane surface molecules, and molecular structure. Hexadimethrine bromide or polybrene is thought to facilitate red cell agglutination by neutralizing the net negative charge between red cells and thus forming ionic bonds between the red cell and the polybrene. An in vitro approach to evaluating the potential clinical impact of a red cell antibody is the monocyte monolayer assay (MMA) that has been used to predict the clinical significance of red cell alloantibodies.