Application of the MultiScreen system to cytokine radioreceptor assays

Radioreceptor assays are becoming increasingly valuable in the biotechnology community for a variety of basic and applied research applications. It is clear, for example, that assessing the potential spectrum of biological activities of a novel polypeptide regulatory factor can be greatly simplified by the development of a rapid radioreceptor assay, since a wide variety of cell types can be screened using a single type of assay. By contrast, searching for potentially diverse biological effects can be an extremely time-consuming process. In addition, screening for agonists/antagonists for hormones using radioreceptor assays has a marked advantage compared with biological assays, in that compounds or natural products that are toxic to cells will not read out as false positives in a binding assay. Our laboratory has developed a major program centered on the molecular characterization of receptors for polypeptide hormones involved in immune regulation, including a number of cytokines/interleukins and also several colony stimulating factors. We have developed a variety of radioreceptor- and fluorescence-based assay systems for ligand-receptor interactions, with applications in basic characterization, purification, cDNA cloning, and drug development screens for cytokine receptors. In this report we compare two assay formats, a standard phthalate oil centrifugation method and a novel plate filtration system, using the interaction between interleukin-1 alpha and its receptor as a test system.