DEVELOPMENT OF A CD28 RECEPTOR BINDING-BASED SCREEN AND IDENTIFICATION OF A BIOLOGICALLY-ACTIVE INHIBITOR

CD28 is a T-cell costimulatory receptor which plays a pivotal role in antigen-induced T-cell response. We have developed a cell-free and sci ntillation-proximity assay-based screen to search for molecules that i nhibit ligand binding to CD28. The assay was shown to be versatile and adaptable to automation for high-throughput screening. Using this ass ay, we identified an inhibitor of CD28, NP2214. The inhibitor was show n to be active in vitro by suppressing IL-2 synthesis and proliferatio n of peripheral blood mononuclear cells in response to CD28 costimulat ion. We also demonstrated the additive effects of NP2214 and cyclospor ine A which act mechanistically distinctly in inhibiting costimulation -induced IL-2 synthesis. (C) 1998 Academic Press.