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

The aim of this work was detect Fcγ 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 × 10^?10 M) giving 25% inhibition in the RIA; unbound AHIgG concentration was then measured in the cell supernatants using RIA. Results show that Fcγ receptors could be detected at 20°C or at 37°C (but not at 4°C) on the four B cell lines tested. At whatever temperature of incubation, Fcγ 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 Fcγ receptor positive cells. It is also useful for detecting Fcγ receptors in membrane preparations or in detergent extracts of human B cell membranes.