Characteristics of an antibody causing agglutination of M-positive non-enzymatically glycosylated human red cells

An alloagglutinin was identified in the serum of an M-negative diabetic patient. The agglutinin reacted with all commercial M-positive red cell samples. Routine crossmatches showed no incompatibility. This anti-M would only agglutinate M-positive red cell samples that had been incubated in 2% glucose for a minimum of 2 h at 37 degrees C, 2 days at 22 degrees C, or 1 week at 4 degrees C. Reactive red cell samples, when washed and incubated in saline, gradually became non-reactive. This antibody reacted optimally in low ionic strength solution at 16 degrees C for 20 min where MM red cells were agglutinated to a titer of 256, score 85; and MN red cells were agglutinated to a titer of 128, score 66. The antibody was denatured by 2-mercaptoethanol and was inhibited by a crude M tryptic isolate and by 2% glucose, but not by other sugars prepared at a 2% concentration.