Extent of desialation of blood group MM, NN, and MN antigens required for reactivity with human anti-T antibody and Arachis hypogaea lectin.

Immunochemical activity of the Arachis hypogaea lectin has been equated, in spite of its different hapten combining requirements, with that of the human anti-T (Thomsen-Friedenreich) antibody population which is of importance in cancer immunology. We show here by gradual desialation of isolated human blood group MM and NN antigens at pH 2.0, 56 degrees C, that A. hypogaea lectin is, in addition, substantially more tolerant to NeuAc in the vicinity of T antigen's immunodominant repeating structures, Gal beta 1 leads to 3 GalNAc, than human anti-T antibodies. Reactivity with the Arachis lectin appeared first at 20-25% release of NeuAc from the antigens, whereas faint reactivity with anti-T was first recognizable at 50-55% NeuAc release from NN and 65-70% from MM antigen. Remarkably, at these degrees of desialation, the NN and MM antigens had about 50% of maximal activity toward the Arachis lectin. The slower appearance of T antigen upon graded desialation of MM antigen is likely due to the higher concentration of NeuAc and difference in some of its linkages on intact MM as compared to NN antigen.