Immunological characteristics of anti-A and anti-B blood group antibodies in the cynomolgus monkey.

Anti-A and anti-B blood group antibodies in the cynomolgus monkey sera were serologically characterized. 2-Mercaptoethanol (2-ME) inactivated these antibodies of both group-A and group-B sera. Furthermore, soluble human ABH substances neutralized these antibody activities. However, these activities were not inhibited by anti-human IgG or IgA serum but by anti-human IgM serum. By gel filtration on Sephacryl S-300, the anti-A and anti-B antibodies reacting readily in saline media were detected in the fractions corresponding to the IgM antibodies. Thus, anti-A and anti-B antibodies in group-B and group-A sera were judged to be mainly of IgM. In contrast to group-A and group-B sera, group-O serum contained IgG antibodies of high titers besides IgM antibodies. Neither 2-ME nor anti-human IgM serum affected these antibody activities. On the basis of the results of the inhibition test using anti-human immunoglobulin sera as well as of gel filtration, group-O sera were divided into the following two categories, the one having only IgG reacting well in the Coombs method and the one having both IgM and IgG.