The influence of MHC class II antigen blockade by perfusion with a monoclonal antibody on rat renal graft survival.

To decrease immunogenicity of the rat kidney, grafts were perfused with an anti-MHC class II monoclonal antibody (mAb). How effectively this procedure blocked class II-positive cells, which were mainly dendritic in appearance, was checked by immunostaining renal sections after perfusion and comparing them with in vitro stained sections. Optimum conditions were applied for graft pretreatment before transplantation. This procedure prolonged graft survival, though not satisfactorily from the biological point of view (9.6 +/- 0.8 versus 7.7 +/- 0.5 days in the control group; P less than 0.02). The dendritic cells were not killed but blocked. Several hours after transplantation, the mAb dissociated from these class II-positive cells. It was also shown that donor cells migrate into the recipient's spleen early after transplantation. The number of these cells was smaller when the transplanted organ was perfused with the mAb. Further studies are suggested to deplete the graft of donor dendritic cells more adequately. They should also combine graft perfusion with anti-class II mAb and recipient immunosuppression at reduced doses.