Antibody Response to Bacteriophage ΦX 174 in Non-Mammalian Vertebrates

After a single injection of 10_8–10 bacteriophage ΦX 174, the chicken, frog and goldfish were shown to produce approximately the same levels of neutralizing, rapidly sedimenting, γ-globulin antibodies as those previously obtained in analogously immunized mammals(5,6). Repeated injections of bacteriophage in the frog and goldfish, at intervals of 2–4 weeks, did not elicit an anamnestic antibody response. However, higher levels of antibody, mainly in the slowly sedimenting γ-globulin fraction were produced after immunization with bacteriophage in complete Freund's adjuvant, and, in the case of the goldfish, after further elevation of the environmental temperature to 32°C. Thus, in 3 classes of non-mammalian vertebrates a change was observed in the sedimentation properties of antibody γ-globulins produced during immunization. This change appeared similar to the replacement of 19S by 7S antibodies in the circulation of immunized mammals. These findings suggest that the mechanisms responsible for this phenomenon were present in the most recent common ancestors of terrestrial vertebrates and bony fish and that formation of rapidly sedimenting antibody is an integral and important part of the immune mechanism.