Binding of Immunoglobulin E to the Receptor on Rat Peritoneal Macrophages

The binding of radiolabeled monomers and chemically cross-linked dimers of rat immunoglobulin E (IgE) to peritoneal macrophages of rats was characterized. With either form, 40,000 to 50,000 molecules of IgE were specifically bound per cell under conditions where no endocytosis occurred. Monomeric IgE dissociated from macrophages within minutes, whereas dimers of IgE had a much slower rate of dissociation. Denatured rat IgE or native human IgE failed to inhibit the binding, but mouse IgE and, to a limited extent, rat IgG did. Oligomers of IgE by virtue of their tighter association with the receptor should prove useful in isolation of the receptor.