Allotypic Suppression in Rabbits: Competition for Target Cell Receptors between Isologous and Heterologous Antibody and between Native Antibody and Antibody Fragments

Neonatal injection with various foreign proteins (normal goat serum, human Cohn fraction II, human albumin) caused a stimulation of immunoglobulin synthesis. This effect was not antigen-specific and did not constitute a conventional antibody response directed against the injected substance. When this stimulatory effect of foreign protein was minimized, the heterologous (goat) anti-rabbit allotype antibody and rabbit antibody F(ab') 2 fragments not only failed to induce suppression but also competed with the suppression-inducing native rabbit antibody. Allotypic suppression in a rabbit can thus only be induced by an antibody molecule possessing an intact Fc portion of isologous, rabbit origin. Antibody to Ae14, an allotypic specificity located on the Fc portion, failed to induce suppression or stimulation of immunoglobulin synthesis. This was attributed to the position of Ae14 in the cell membrane which reduced its accessibility to antibody.