HAPTEN-MEDIATED IDENTIFICATION OF CELL-MEMBRANE ANTIGENS USING AN ANTI-FITC MONOCLONAL-ANTIBODY

A monoclonal anti-FITC antibody (F4/1) was produced and demonstrated t o be specific for both the free and protein-conjugated (either soluble or cell-bound) form of fluorescein, or carboxyfluorescein. When mouse thymocytes were labelled with a novel fluorescein derivative 5(6)-car boxyfluorescein succinimidyl ester (CFI-NSE), the incorporation of flu orescein was predominantly membrane-bound as demonstrated immunohistoc hemically. The coupling of CFI-NSE to cells displayed a random distrib ution pattern as shown by immunoblotting of cell extracts prepared by detergent solubilization of CFI-NSE-labelled thymocytes. In addition, the Thy-1.2 antigen immunoprecipitated from a CFI-NSE-labelled thymocy te lysate with a rat monoclonal antibody (Mab) could be detected using the anti-FITC Mab. The molecular weight of the immunoprecipitated mat erial could be estimated immediately by reference to the FITC-labelled molecular weight markers electrophoresed simultaneously.