Neural precursor cells (NPC) may provide a source for restaurative therapy. We wanted to study the immunogenic potential of human NPC. We transplanted human NPCs with or without cyclosporine A (10 mg/kg) expanded in serum-free conditions into the striatum of rats unilaterally lesioned with 6-hydroxydopamine. Four months after transplantation, there was significant improvement of amphetamine-induced rotational behavior 9 non-immunosuppressed (13.1+/-4.9 pre vs 8.5+/-4.0 after grafting) but nor for 11 animals immunosuppressed with CyA (12.3+/-1.7 vs 11.3+/-2.8). The number of TH-IR cells was comparable in both groups (1,580+/-700 vs 1,274+/-295). All grafted animals only showed mild activation of astrocytes and macrophages within the graft. There was no evidence for tumor formation. Immunosuppression of rats, xenotransplanted with human NPC did not improve graft survival or function.