Fluorescence sandwich enzyme-linked immunosorbent assay for detecting human interleukin-2 receptors

A very sensitive fluorescence sandwich enzyme-linked immunosorbent assay (FS-ELISA) for the detection of soluble and cell-associated human interleukin-2 receptors (IL-2R) has been developed. For use in this assay system, two anti-human IL-2R monoclonal antibodies, H 48 and biotinylated HA 26, were selected from six monoclonal antibodies directed against different epitopes on the IL-2R molecule. The FS-ELISA specifically detected human IL-2R in both the culture supernatants and cell lysates of human IL-2R-bearing cells and the assay displayed a 10(3)-fold increase in sensitivity over the usual colorimetric IL-2R ELISA. The IL-2R molecules in supernatants and lysates of the PHA-stimulated mononuclear cells were of 50,000 and 60,000 molecular weight, respectively, as estimated by size exclusion high performance liquid chromatography.