Idiotypes of pre-existing human anti-carcinoma anti-T and anti-Tn antibodies.

All humans normally possess antibodies, predominantly IgM, that react specifically with the Thomsen-Friedenreich (T) and the Tn antigens which are present in immunoreactive form on > 85% of all human carcinomas, but not in healthy and otherwise diseased tissues. We report here a serological study of idiotype expression and antigen reactivity of the anti-T and anti-Tn antibodies. Idiotypy was analyzed with rabbit antibodies raised against, and made specific for, affinity-purified polyclonal anti-T and anti-Tn antibodies from blood group A1B healthy adult donors. Anti-T and anti-Tn antibodies cross-reacted idiotypically in spite of their distinct epitope specificities. By adsorbing anti-T antibodies on insolubilized synthetic T carbohydrate we could firmly link idiotype expression with antigen reactivity. The relation of idiotype expression to the antigen-binding site of plant seed lectins was also studied; one originated from Arachis hypogaea [peanut agglutinin (PNA)], the other from Artocarpus integrifolia (Jacalin). PNA inhibited only anti-T antibodies. Jacalin inhibited both anti-T and anti-Tn antibodies in a dose-dependent manner. Neither idiotypic nor anti-idiotypic antibodies diminished the binding of lectins to T and Tn epitopes. The shared idiotypes on natural anti-T and anti-Tn antibodies permit consideration of application of their anti-idiotypes in treatment and/or prevention of human carcinoma.