Covalent cross-linking of subunits of the receptor for immunoglobulin E induced by immunoprecipitation.

The receptor on rat basophilic leukemia and related normal cells that binds monomeric immunoglobulin E (IgE) with high affinity contains four polypeptide chains: alpha (to which the IgE binds), beta, and a disulfide-linked dimer of gamma chains. In this study, we have analyzed a further component variably seen when the purified receptors are analyzed on polyacrylamide gels. This component has an apparent Mr of approximately 43 000 and, after treatment with reducing agents, yields one beta and two gamma chains. This complex is generated by immunoprecipitation of preparations totally lacking in it. This novel in vitro phenomenon has provided additional information about the structure of the receptor. Its possible relationship to in vivo aggregation that triggers degranulation of the cells is of interest.