Low-affinity receptor for IgE (FcERII, CD23) and its soluble fragments.
The low-affinity receptor for IgE (FcERII or CD23) is a membrane 45-kD glycoprotein which is cleaved by an autoproteolytic mechanism into soluble 37-, 33- and 25-kD fragments that are capable of binding to IgE (IgE-binding factors, IgE-BFs). FcERIIa (which is expressed only on fresh B cells) differs from FcERIIb (which is expressed on IL4-stimulated B cells, monocytes, eosinophils and T cells) by a few intracytoplasmic amino acids. The only function of FcERII which is clearly demonstrated is the IgE-dependent cytotoxicity of FcERIIb on monocytes and eosinophils. We here review our recent observations indicating that 37-kD IgE-BFs regulate the synthesis of human IgE. Recombinant 37-kD IgE-BFs increase the IL4-induced synthesis of IgE by peripheral blood lymphocytes, as well as the IL4-independent, ongoing synthesis of IgE by either in vivo activated B cells from allergic patients or by in vitro IL4-preactivated B cells.
Delespesse
G
G
University of Montreal, Notre-Dame Hospital, Research Center, Canada.
Hofstetter
H
H
Sarfati
M
M
D015703:Antigens, CD / Q000032:analysis*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis* / Q000502:physiology; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism*; D015847:Interleukin-4 / Q000494:pharmacology; D010446:Peptide Fragments / Q000032:analysis* / Q000502:physiology; D011961:Receptors, Fc / Q000032:analysis* / Q000502:physiology; D017455:Receptors, IgE
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D010446:Peptide Fragments; D011961:Receptors, Fc; D017455:Receptors, IgE; D015847:Interleukin-4; D007073:Immunoglobulin E