Immunosuppressive effect on T cell activation by interleukin-16-cDNA-transfected human squamous cell line

It is well known that it is difficult to induce an immunotolerance with all ogeneic skin transplantation. We attempted to find the immunosuppressive pr otocol for prolonging skin allograft rejection by using interleukin-16 beca use IL-16 is considered one of the natural ligands to CD4 molecules. First we examined whether synergistic immunosuppressive effects of recombinant IL -16 plus anti-CD4 mAbs are induced in mixed lymphocyte reaction (MLR). Next we used IL-16-cDNA-transfected OSC-20 (human oral squamous cell carcinoma cell line) as an in vitro model of the epidermal keratinocyte equivalent an d examined whether this transfectant could inhibit the activation of alloge neic T cells. Our data indicated that IL-16 clearly inhibited human MLR and that IL-16 increased synergistically the immunosuppressive effect of anti- CD4 mAb. We also used IL-16 transfectant and this produced more than 50 ng/ ml of IL-16 in the supernatant by which human MLR was significantly inhibit ed. Furthermore, this transfectant also inhibited the activation of allogen eic lymphocytes stimulated directly with transfectant cells. These results indicated that the IL-16-producing allogeneic skin graft might have a local immunosuppressive action that would prolong graft survival. (C) 2000 Acade mic Press.