Nerve allotransplantation has been used successfully in human subjects to restore function after traumatic nerve injury and avoid subsequent limb amputation. However, due to the morbidity associated with nonspecific immunosuppression, this reconstructive approach has been limited to patients with particularly severe nerve injuries. It would be desirable to broaden the indications for such procedures through development of less toxic antirejection therapies. A miniature swine model of nerve transplantation was used to investigate the effects of preoperative ultraviolet-B (UV-B)-irradiated donor alloantigen portal venous infusion and injection of cultured major histocompatibility complex (MHC)-matched Schwann cells into the nerve graft. The transplanted ulnar nerves were harvested at 20 weeks. Histomorphometry showed marked enhancement in nerve regeneration through allografts injected with Schwann cells. Serial mixed lymphocyte assays demonstrated suppression of the recipient immune response to the donor antigen after pretreatment, but no additional neuroregenerative effect of donor alloantigen pretreatment.