LACZ INDUCIBLE, ANTIGEN MHC-SPECIFIC T-CELL HYBRIDS

The nuclear factor of activated T cells (NFAT) enhancer element of the IL-2 gene can regulate expression of the Escherichia coli lacZ report er gene in activated T cells. Based upon this observation, we showed t hat this inducible NFAT - lacZ construct could be used to measure TCR mediated, ligand-specific activation in single T cells. Here we descri be a general approach to obtaining lacZ inducible, T cell hybrids by g enerating two new fusion partners BWZ.36 and BWZ.36 CD8alpha derived b y transfecting alpha-beta-BW5147 cells with the NFAT - lacZ construct. Using these fusion partners and normal T cells from immunized mice, w e obtained T cell hybrids in which lacZ activity is specifically induc ed in response to antigen/MHC class II or MHC class I complexes. We sh ow that measuring ligand induced T cell activation by the non-radioact ive lacZ assay is simpler, faster, and more cost-effective relative to conventional IL-2 assays. Most importantly, the unique ability to det ect activation of single T cells by the lacZ assays permits detection of rare antigen presenting cells and thus provides the basis for devel oping expression cloning strategies for identifying unknown T cell ant igens.