title: Relationship between human IgE-binding factors (IgE-BF) and lymphocyte receptors for IgE.
abstract: This study indicates that human IgE-binding factors (IgE-BF) found in the cellfree culture supernatant (CSN) of Fc epsilon R-bearing B cells are breakdown products of the surface Fc epsilon R. This conclusion is suggested by the following observations. 1) Fc epsilon R and IgE-BF share several antigenic determinants as shown by immunoprecipitation with several Mab to Fc epsilon R (MabER) and SDS-PAGE analysis of the precipitates. 2) Upon incubation at 37 degrees C, normal tonsillar lymphocytes lose their Fc epsilon R and this is associated in a time-related manner with the release in the CSN of molecules reacting with two MabER. 3) Surface radioiodinated tonsillar lymphocytes or RPMI 8866 cells release labeled IgE-binding molecules displaying the same antigenic composition and the same migration on SDS-PAGE as purified IgE-BF. 4) Peptide mapping of highly purified IgE-BF and Fc epsilon R reveals the presence of several identical fragments after digestion with either alpha-chymotrypsin, trypsin, or papain. Moreover, papain digestion of the 25-27 kD IgE-BF and of the affinity-purified Fc epsilon R, generated a 15 kD fragment reacting with two MabER and that is known to bind IgE. Although these data strongly suggest that IgE-BF may be directly derived from cell surface IgE receptors, they do not exclude the possibility that some IgE-BF may also be secreted without being first anchored in the cell membrane.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D001402:B-Lymphocytes / Q000032:analysis*; D002460:Cell Line; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism*; D008222:Lymphokines / Q000276:immunology / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D014066:Palatine Tonsil / Q000166:cytology; D010446:Peptide Fragments / Q000276:immunology / Q000302:isolation & purification; D010447:Peptide Hydrolases; D010449:Peptide Mapping; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc / Q000276:immunology / Q000378:metabolism*; D017455:Receptors, IgE
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D008222:Lymphokines; D008565:Membrane Proteins; D010446:Peptide Fragments; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc; D017455:Receptors, IgE; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors; D007073:Immunoglobulin E; D010447:Peptide Hydrolases