The μ- and κ-chains from four human cold agglutinins having anti-I specificity have been analysed:
The κ-chains have either Asp or Glu, but not both, at the N-terminus. This provides additional support for the view that cold agglutinins are of monoclonal origin.
Both heavy and light chains from cold agglutinins vary as much in amino acid composition as do monoclonal chains of a given type chosen at random. The chemical individuality of cold agglutinin μ-chains is shown also by differences in hexose, fucose and glucosamine content.
The apparent lack of correlation between overall antibody activity and chemical composition of constituent peptide chains indicates the need for close definition of combining specificity in structural studies of cold agglutinins.