Detection of Fc gamma receptors on human lymphoblastoid cell surfaces using a simple solid phase radioimmunoassay specific for human IgG.

The aim of this work was to detect Fc gamma receptors on human lymphoblastoid cells using a solid phase radioimmunoassay (RIA), specific to human IgG. RIA was performed by coupling rabbit anti-human IgG (AHIgG) to acrylamide beads to make immunobeads. The specificity and sensitivity of binding of human [125I]IgG to immunobeads permitted detection of as little as 10(-10) M unlabeled human IgG or aggregated human IgG (AHIgG) in competitive assay. The cells were incubated with an AHIgG concentration (3 x 10(-10) M) giving 25% inhibition in the RIA; unbound AHIgG concentration was then measured in the cell supernatants using RIA. Results show that Fc gamma receptors could be detected at 20 degrees C or at 37 degrees C (but not at 4 degrees C) on the four B cell lines tested. At whatever temperature of incubation, Fc gamma receptors were not detected on three T cell lines nor on two 'non T-non B' cell lines. This method allows screening of a large number of Fc gamma receptor positive cells. It is also useful for detecting Fc gamma receptors in membrane preparations or in detergent extracts of human B cell membranes.