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Thermal regulation of the immune response was studied in toads following single injections of bacteriophage f2. The immune response was markedly inhibited in animals kept at 15° as compared to the controls (25°). The appearance of serum antibodies was delayed in animals kept at 15° for the first post-immunization week but their peak antibody levels were similar to those in toads maintained at 25° throughout. Transfer of animals from 25° to 15° 2 weeks after immunization only temporarily depressed the serum antibody levels but caused a marked delay in conversion from heavy to light antibodies. Our results are in keeping with the hypothesis that lowered environmental temperatures inhibit a variety of metabolic processes which may be concerned with the utilization of antigen and/or the synthesis of antibodies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]