Cross reactivities among some mammalian haptoglobins studied by a monoclonal antibody

Mouse monoclonal antibody antihuman-Hp, product of clone 2.36.71.41 was found to recognize, however, with different affinities, the immunological determinant on haptoglobin of some mammals (goat, sheep, cow, horse, rabbit). The following differences in immunological cross reactivities were noticed: (i) haptoglobins present in sera of goat, sheep and cow (Artiodactyla, Bovidae) react in enzyme-linked immunosorbent assay (ELISA) and form precipitates in agarose gel; (ii) horse (Perissodactyla) and rabbit (Lagomorpha) haptoglobins react in ELISA, but they do not form precipitates; and (iii) haptoglobins of dog, fox, cat (Carnivora) and pig (Artiodactyla, Suidae) are not recognized by the tested monoclonal antibody either in ELISA or in agarose gel. This study suggests that monoclonal antibody, clone 2.36.71.41, recognizes the structure on haptoglobin around the disulphide bond linking two alpha chains. Antigenic structure of Bovidae haptoglobins is rather similar to human haptoglobin 2-2 (circular polymers) than to 2-1 type (linear polymers). Monoclonal antibody 2.36.71.41 could be used for classification of mammalian haptoglobins by epitope structure. It can distinguish polymeric haptoglobins similar to human type 2-2 from other mammalian haptoglobins.