Endowing T cells with antibody specificity using chimeric T cell receptors

T cells recognize antigen in the form of a peptide associated with a cell surface molecule encoded by the major histocompatibility gene complex (MHC). The elaborate requirements for the T cell receptor (TCR)-antigen interaction stand in contrast to the simple and defined nature of the antigenic determinants recognized by antibodies. The similarity in the molecular structure and gene organization between antibodies and the TCR has prompted attempts to interchange the antigen-binding, variable regions of these molecules. To this end, chimeric TCR (cTCR) genes, composed of the variable domains of antibodies linked to TCR constant regions, have been used to confer antibody-type specificity on T cells. cTCR-expressing T cells respond to stimulator cells as well as to immobilized antigen in an MHC unrestricted and independent manner. The antibody-like specificity of the resulting T cells has been exploited, using defined ligands, to elucidate the physicochemical parameters that govern TCR-mediated signaling, and to provide a useful experimental system to study the role of MHC and cell-adhesion/accessory molecules in T cell activation. The successful expression of such cTCR in transgenic mice opens new avenues to explore the role of the MHC in T cell development and maturation. Eventually, chimeric receptors specific to tumor or viral antigens might be used for in vivo targeting of T cells in the framework of immuno- and gene therapy.