Sandwich Solid Phase Radioimmunoassays for the Characterization of Human Immunoglobulins Synthesized In Vitro

Abstract

This report describes a sensitive, simple and rapid direct-binding solid phase sandwich radioimmunoassay for measurement of intrinsically labeled immunoglobulins synthesized in vitro. With the direct technique, small volumes of labeled tissue culture supernatants or cell sonicates can be placed directly in the sandwich assay tubes and, after a short incubation and washing, the bound specific antigen can be counted. This new direct assay complements the previously described sandwich inhibition radioimmunoassay for immunoglobulin quantitation. With the use of both techniques on the same samples, detailed quantitative characterization of cellular synthesis, assembly and secretion of immunoglobulins can be obtained under a variety of circumstances. The quantity, absolute specific activity and antigenic composition of immunoglobulins synthesized in vitro can be determined routinely with the application of the two sandwich techniques. A series of experiments on plasma cells that synthesize monoclonal IgG illustrate applications of the methods. The sandwich techniques are applicable to the detection of unlabeled or labeled immunoglobulins in the nanogram to microgram range and are suited to studies of in vitro immunoglobulin synthesis where such sensitivity and specificity are required.