The cytolytic T lymphocyte (CTL) specifically recognize and kill by direct lysis target cells which are diseased or foreign. The clinical benefits of manipulating the CTL response are clear, however, safe manipulation will almost certainly require an understanding of CTL-target cell recognition at the molecular level. Other than the qualitative requirement of foreign antigen and MHC proteins, target cell components necessary for optimal CTL recognition have not been defined. The overall aim of this project is to more precisely define the receptor ligand interactions between membrane proteins on the CTL and target cell. We will do this by constructing and using a new type of lipid vesicle (an artificial target cell) which is cell size and has a sealed outer membrane. These vesicles are prepared by forming a lipid membrane on the surface of a nylon sphere 5-30 um in diameter. In initial experiments, we have used anti-CD3 monoclonal antibody covalently attached to these vesicles to trigger CTL and demonstrated CTL mediated permeability changes in the vesicle membrane. We have also developed an approach for examining receptor ligand interactions by incorporating cell surface proteins into the artificial target cell (ATC) membrane and examining cell-ATC adhesion. Using this approach we have shown directly that LFA-3 is a ligand for the T cell surface protein CD2. We hope to use this methodology to biochemically define receptor-ligand interactions. These studies should result in a better understanding of the molecular basis of CTL-target interaction and serve as a basis for designing a vaccine able to trigger an in vivo response.
