Effects on blood group antigens from storage at low ionic strength in the presence of neomycin

Red blood cells (RBC) stored without plasma in a neomycin, low ionic strength medium at 4 degrees C in excess of 24 h show alterations in antigen reactivity. There is a loss of protease-sensitive RBC antigens and a protease-type increased IgG saline agglutinability of Rh antigens that is associated with increased binding of 125I anti-D. Both the serological findings and the alteration in RBC membrane polypeptides are consistent with protease modification of the membrane due to contamination of the RBC by leukocytes. Neomycin, low ionic strength or leukocytes alone or in dual combination do not produce the observed changes in antigen reactivity. The role of neomycin and low ionic strength in this phenomenon and implication for quality control of reagent RBC used for antibody detection and identification are discussed.