Specific T cell deletion by transfected human monocytes expressing fas ligand and antigen

The aim of our experiments was to determine whether deletion of antigen specific T helper cells could be accomplished by delivering the antigenic peptide to antigen presenting cells. Tetanus toxin peptide residues 830-843 was chosen for these experiments. Two mammalian expression vectors carrying the genes for human Fas ligand and a chimeric invariant chain-tetanus toxin peptide construct were designed. The T cell proliferative response to tetanus toxoid was inhibited when the antigen was presented by autologus monocytes transfected with Fas ligand. T cell mixture experiments using two syngeneic T cell lines specific either for tetanus toxoid or for pertussis toxin demonstrated that the killing effect elicited by the antigen pulsed/Fas ligand-transfected antigen presenting cells was antigen specific. Finally, we demonstrated that transient expression of antigen delivered by plasmid DNA can substitute for soluble antigen in the induction of antigen-specific T cell responses. Antigen presenting cells transfected with the vector carrying Fas ligand and the vector carrying the chimeric invariant chain-peptide antigen gene were shown to inhibit antigen specific T cell reactivity. This strategy may be useful for the induction of apoptosis in allopeptide reactive T cells driving chronic rejection.