Alloantigen specific deletion of primary human T cells by Fas ligand (CD95L)‐transduced monocyte‐derived killer‐dendritic cells

Numerous studies have been performed in vitro and in various animal models to modulate the interaction of dendritic cells (DC) and T cells by Fas (CD95/Apo‐1) signalling to delete activated T cells via induction of activation‐induced cell death (AICD). Previously, we could demonstrate that Fas ligand (FasL/CD95L)‐expressing ‘killer‐antigen‐presenting cells’ can be generated from human monocyte‐derived mature DC (mDC) using adenoviral gene transfer. To evaluate whether these FasL‐expressing mDC (mDC‐FasL) could eliminate alloreactive primary human T cells in vitro, co‐culture experiments were performed. Proliferation of human T cells was markedly reduced in primary co‐cultures with allogeneic mDC‐FasL, whereas a strong proliferative T‐cell response could be observed in co‐cultures with enhanced green fluorescent protein‐transduced mDC. Inhibition of T‐cell proliferation was related to the transduction efficiency, and the numbers of mDC‐FasL present in co‐cultures. In addition, proliferation of pre‐activated alloreactive CD4+ and CD8+ T cells could be almost completely inhibited in secondary co‐cultures using mDC‐FasL as stimulatory cells, which was the result of induction of apoptosis in the majority of preactivated T cells. The specific deletion of alloreactive T cells by mDC‐FasL was confirmed by an unaffected proliferative response of surviving T cells towards allogeneic ‘third‐party’ peripheral blood mononuclear cells in a third stimulation, or upon unspecific stimulation with anti‐CD3/CD28 beads. The results of this study demonstrate that allospecifically activated T cells are efficiently eliminated by mDC‐FasL, supporting further investigations to apply FasL‐expressing ‘killer‐DC’ as a novel strategy for the treatment of allograft rejection.