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 reporter gene in activated T cells. Based upon this observation, we showed that this inducible NFAT-lacZ construct could be used to measure TCR mediated, llgand-speclflc activation in single T cells. Here we describe a general approach to obtaining lacZ inducible, T cell hybrids by generating two new fusion partners BWZ.36 and BWZ.36 CD8α derived by transfectlng α-β-BW5147 cells with the NFAT-lacZ construct. Using these fusion partners and normal T cells from Immunized mice, we obtained T cell hybrids in which lacZ activity Is specifically induced in response to antlgen/MHC class II or MHC class I complexes. We show that measuring llgand induced T cell activation by the non-radioactive lacZ assay Is simpler, faster, and more cost-effective relative to conventional IL-2 assays. Most Importantly, the unique ability to detect activation of single T cells by the lacZ assays permits detection of rare antigen presenting cells and thus provides the basis for developing expression cloning strategies for Identifying unknown T cell antigens.