1 The Department of Pediatrics, New York University College of Medicine, and New York Foundling Hospital, New York City.
Twenty-three infants from 2 weeks to 6 months old, all of whom had measurable titers of transplacentally-received diphtheria antitoxin, were immunized with a single injection of diphtheria toxoid on alum.
Infants with a low level of passive transplacental antibody were able to respond as well or almost as well as infants who had no passive transfer. The formation of circulating antibody was depressed in infants with a high titer of passively received antibody.
It is suggested that the amount of interference with active immunization is dependent on the relation of the titer of passive transfer and the potency of the antigen. The application of this principle is indicated.
Submitted on January 7, 1952