Characterization of the target cell receptor for IgE. V. Studies with an antiserum specific for the receptor

Previous studies had shown that isolation of the receptor for IgE from rat basophilic leukemia (RBL) cells by means of IgE-sepharose yiels two surface components having apparent m.w. of 55,000 and 45,000 daltons. In the present study, an antiserum to such a receptor preparation was induced in a rabbit. This antiserum, even though it could not initiate histamine release in vivo or in vitro, reacted with the RBL cell surface components bound to and eluted from IgE-Sepharose, as well as with these two components present in detergent extracts of surface-labeled RBL cells. It was also capable of reacting with IgE-receptor complexes. With this antiserum, it was possible to demonstrate that, when occupied by IgE, the 45,000 dalton component cannot be surface iodinated, whereas the 55,000 dalton component can. Moreover, it could be shown that both components are present in detergent lysates of surface-iodinated peritoneal rat mast cells (RMC). The results have also indicated that the 55,000 and 45,000 dalton components are present on both intact RMC and RBL cells. Moreover, the antibodies to the 45,000 dalton receptor component appeared to react with those parts of the receptor that do not make contact with IgE.