The Binding of Human Immunoglobulin G1 Monomer and Small, Covalently Cross-Linked Polymers of Immunoglobulin G1 to Human Peripheral Blood Monocytes and Polymorphonuclear Leukocytes

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Abstract

Covalently cross-linked dimers and oligomers composed of 2-4 subunits of monoclonal human IgG1 were prepared by incubation of purified monomeric IgG1 with glutaraldehyde followed by gelfiltration chromatography. Monomers, dimers, and oligomers then were labeled with 125I and used to compare the binding properties of IgG Fc receptors on human peripheral blood monocytes and polymorphonuclear leukocytes (PMN). Binding of IgG1 to monocytes at 37°C and of IgG1 polymers to PMN at 4°C could be readily measured and were found to be reversible and saturable. Scatchard plots of binding were linear in each instance. Monocytes bound a mean of 20,200±6,800 molecules/cell of IgG1 monomer at saturation and comparable amounts of dimer or oligomer. The mean association constant (Ka) for binding of IgG1 monomer to monocytes was 8.6 × 108M−1 and the Ka for binding of dimer and oligomer were three-to fivefold greater.

Authors

Roger J. Kurlander, Janet Batker