Cold-induced augmentation of I blood group antigen interactions with galactophilic lectins

The I antigen appears on human cells in the postnatal period, by addition o f N-acetyllactosamine (beta 1-6) branching to the fetal i antigen structure , which is specified by linear oligo N-acetyllactosamine (beta 1-3) chain. Concurrently with the I antigen appearance on adult human erythrocytes most human sera exhibit low levels of anti-I agglutinins. These antibodies indu ce hemagglutination mainly at low temperatures (4 degrees C) and scantly at body temperature. Therefore they were named "cold agglutinins". We have us ed these antibodies and several hemagglutinating galactophilic animal, plan t, and microbial lectins that also react with the I antigen, to study wheth er the cold-favored agglutination of the I antigen-bearing cells is a pecul iar property of the anti-I antibodies or a special trait of that antigen. I t has been found that the interactions of all of the examined lectins, irre spective of their source, with the adult human erythrocytes significantly i ncreased at 4 degrees C, in contrast to those of the same cells with divers e I-insensitive antibodies and lectins, which were significantly higher at room temperature.