Macrophage receptors for IgE: binding of IgE to specific IgE Fc receptors on a human macrophage cell line, U937.

Open Access
Publisher Website
Google Scholar
Abstract
Human IgE was found to bind to the human macrophage line U937. Binding was specific for IgE in that it was inhibited by 3 different human IgE myeloma proteins and by Fc fragments prepared from IgE, but not by IgE Fab fragments or by myeloma proteins representative of the 4 IgG subclasses or by a rat IgE myeloma protein. Dissociation and association rates were rapid, with estimated t1/2 of less than 1 min. The Ka was 4.15 X 10(7) liter/mol. Between 53,000 and 93,000 sites per cell were calculated. The U937 receptor for IgE was trypsin sensitive, whereas the receptor for IgG on the same cell was relatively trypsin resistant.