Immunochemical relationship between Forssman and globoside glycolipid antigens

The rabbit antibody response to the human blood group P glycolipid antigen, globoside, GalNAc(beta 1-3)Gal(alpha 1-4)Gal(beta 1-4)Glc-Cer, has been examined with respect to cross-reactions with the structurally related Forssman glycolipid GalNAc(alpha 1-3)GalNAc(beta 1-3)Gal(alpha 1-4)Gal(beta 1-4)Glc-Cer. Immunoadsorbent columns were used to isolate three purified antibody populations from the anti-globoside sera: (1) fraction A, antibodies that cross-react with both glycolipids; (2) fraction B, antibodies that react with Forssman antigen but not with globoside; and (3) fraction C, antibodies that are specific for globoside. The proportion of each fraction in the total antibody response to globoside appears to be related to preexisting immunity to these antigens. A rabbit with a high preimmune titer to Forssman antigen produced a large amount of Forssman-specific antibody, whereas a rabbit with a low or nonexistent preimmune titer of anti-Forssman antibody produced large amounts of globoside-specific antibody. The presence of Forssman-specific antibody in an immune response to globoside is an example of a heteroclitic type of immune response.