The role of N K T Cells in Transplantation

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Natural killer T cells in this model were shown to induce accelerated rejection. This effect could be specific for the NK cells or would be the results of a cooperation between the NK cells (secretion of cytokines) and T cells (as allocytotoxic effectors). From our study, not only T cells but also NK cells may play a role in organ transplantation rejection. NK-T cells may induce immune tolerance in organ transplantation. However, this mechanism using specific immune therapy for the induction of tolerance or to increase anti-cancer cytotoxic activity needs further study. These data confirm the inhibitory role of host NK cells in stem cell allogeneic engraftment. We have demonstrated the beneficial effect of anti-NK treatment. Treatment with anti-asialo-GM1 provides a means for improving the immunologjc conditioning of the recipient and showed no harmful effects. NK-cell activity was actually restored a few week after a brief inhibition, which may contribute strongly to maintaining a stable chimerism. Our data are comparable to those obtained with a lethally irradiated model reconstituted by more important semi-allogeneic FLCT mixed with a mature T-cell donor-which became activated and released cytokines. CD3^+ /CD56^+ cells, low in freshly isolated UCB, proliferated significantly in bulk MLC and represented a majority of the responders after single cell cloning. These cells expressed the CD8^+ phenotype and a few N-specific cells proliferated and exhibited an MHC-restricted killing activity. Cytokine production on the UCB clones was lower than in the PB clones, despite their stronger killing activity. The CD3^+ CD8^+ T cells, expressing, the CD56^+ marker, could be the major cells responsible for title induction of GVHD. They should be proven in HLA-mismatched UCB transplantation.