Primary and secondary immune responses of the marine toad (Bufo marinus) to bacteriophage f2.

The primary and secondary immune responses of toads (Bufo marinus) were studied using the bacteriophage f2 as antigen. Antibodies were identified in the serum 2 weeks after primary immunization and peak antibody levels were reached at 6 weeks. Although both IgM and IgG antibodies can be found in toad serum, most of the antibody activity in our animals persisted in the IgM fraction until 8 weeks after immunization. When a second injection of antigen was given 4 weeks after primary immunization, there was a marked increase in the total serum antibody activity and IgG antibodies were found as early as 4 weeks after the second injection of antigen. These observations suggest that the toad, B. marinus, is capable of a true secondary response to the bacteriophage f2.