The Immunoglobulin Structure of Human Anti‐M Agglutinins

Fifty examples of human anti-M agglutinins were subjected to reductive cleavage using both 2-mercaptoethanol (2-ME) and dithiothreitol (DTT). Thirty-nine (78%) were resistant to inactivation by sulphydryl compounds indicating IgG composition. This was confirmed by column chromatography. The remaining eleven sera were sensitive to reduction cleavage. There was no obvious association of immunoglobulin composition of the antibody with previous immune exposure to the M antigen. These results confirm observations in the literature that anti-M agglutinins are an exception to the generally expected correlation of saline agglutinating activity with IgM structure.