Immune response in Xenopus laevis and immunochemical properties of the serum antibodies.

Antibody production in the African clawed toad () against Salmonella flagella and the immunochemical properties of the antibodies were studied. The titre of the serum antibodies increased slowly and reached a maximum at 3 weeks after immunization and they were detectable even 20 weeks after antigenic stimulation. No protein components were electrophoretically demonstrated at the region corresponding to the IgG of mammalian antibodies. Two types of antibodies were found; the one produced early after immunization was heat-labile and the other produced later was heat-stable. The former was of low molecular weight (7S component) and the latter was macromolecular (19S component). Both antibodies moved electrophoretically to the cathode and were sensitive to 2-mercaptoethanol (2-ME) treatment, and their antigenicities were not identical. The low molecular weight antibody did not fix complement in the presence of antigen, in contrast to the macromolecular antibody. The low molecular weight antibody did not correspond to the IgG type of mammalian antibodies in the following properties; 2-ME sensitivity, heat-sensitivity, electrophoretic mobility and absence of complement-fixing ability.