Radioassays of blood group M, N and T (Thomsen-Friedenreich) antigens.

Radioassays employing the double-antibody or Farr techniques were developed for the M, N and T antigens. Blood group glycoproteins were isolated by butanol extraction of red cell stroma and iodinated by the chloramine-T technique. The final purity of glycoprotein was over 75% as judged by radioimmunoassay (RIA). T activation of glycoprotein was obtained with neuraminidase. A specific RIA was obtained for the M antigen and was sensitive to approximately 10 ng of glycoprotein or glycopeptide. In the RIA system rabbit anti-M displayed a higher affinity for M glycoprotein than for M glycopeptide. A RIA that was entirely specific for the N antigen, could not be obtained. A radioassay, obtained for the T antigen with peanut agglutinin in the Farr technique, was sensitive to approximately 100 ng of T antigen and was readily inhibitable by monosaccharides. A RIA, obtained for the T antigen with rabbit anti-T, was entirely specific and sensitive to approximately 1 ng of T activated glycoprotein or glycopeptide but was not inhibitable by monosaccharides.