The immune detection and quantitation of antigenic cell-free Fc receptor by solid phase RIA employing monoclonal anti FcR antibody.

A solid phase radioimmunoassay for cell-free antigenic mouse Fc receptor (FcR) was developed, using an 80% acetone solution for fixation of relatively large amounts of protein on PVC microtiter plates. Purified 125I labelled monoclonal anti FcR (125I-aFcR) secreted by the 2.4G2 hybridoma was used for detection and quantitation of the bound receptor. Concentrations of cell-free FcR in NP-40 extracts of FcR expressing cells were calculated from the linear part of a standard curve and expressed in units of antigenic activity - one unit being the amount of antigen capable of binding 1 microgram of 125I-aFcR. This method can be used for detecting cell-free FcR as a minor constituent in a mixture of proteins.