Preferential expression of anti-bovine serum albumin IgE homocytotropic antibody synthesis and anaphylactic sensitivity in the neonatal rabbit

The phenotypic expression of the genetic capacity to synthesize anti-bovine serum albumin (BSA) IgE homocytotropic antibody and later to develop systemic anaphylactic sensitivity to BSA was studied in the neonatal rabbit. Newborn rabbits immunized with soluble bovine serum albumin were rendered totally immunologically unresponsive to BSA. In contrast, newborn rabbits immunized with alum-precipitated BSA or with soluble BSA in conjunction with a Corynebacterium parvum adjuvant produced only anti-BSA IgE homocytotropic antibody during the neonatal period and throughout adult life; these rabbits did not produce anti-BSA antibody that could be detected by the passive hemagglutination or antigen-binding techniques. Immunization of the 7-day-old rabbit with soluble BSA induced immunologic unresponsiveness to BSA with the exception of anti-BSA IgE homocytotropic antibody that was preferentially produced when these rabbits were adults. When alum-precipitated BSA or soluble BSA together with C. parvum was administered to the 7-day-old rabbit, anti-BSA antibodies were produced that were detected by all of the immunologic test procedures. Although anti-BSA IgE homocytotropic antibody could be produced in adult rabbits receiving primary or secondary injections of alum-precipitated BSA, systemic anaphylactic sensitization to BSA developed in only 3 of 32 animals. However, of 36 adult rabbits that developed anti-BSA IgE homocytotropic antibody as a result of neonatal exposure to BSA, 31 developed systemic anaphylaxis to BSA. We conclude that the genetic potential to synthesize specific, IgE homocytotropic antibody and to develop systemic anaphylactic sensitivity can be phenotypically expressed in the neonatal rabbit.