Duration of Passive Immunity. Part III

Abstract

1. The course of disappearance of passive immunity in rabbits injected with diphtheria antitoxin obtained from goats, men, guinea-pigs and cows, consists of the same three phases that follow the injection of horse serum. 2. The rabbits examined were more responsive to goat, human and guinea-pig serum than to horse and cow serum. 3. The course of disappearance of passive immunity in rabbits, horses and guinea-pigs injected with homologous antitoxin, consists of Phases A and B only, and Phase B is far slower than when heterologous serum is injected into rabbits. 4. Sheep and goats eliminate antitoxin obtained from a horse at a very slow rate, and Phase C is hardly detectable. 5. Natural immunity of horses to diphtheria toxin is gradually acquired by a number of increasing responses to external stimuli.