Currently, regulation of immune response after grafting has become a hot topic in Parkinson's disease (PD) transplantation research. Interleukin-10 (IL-10) is an important regulator of immune system. Presently, we transplanted c17.2 neural stem cells transfected with pcDNA3.1-Hygro-IL-10 vector (IL-10-c17.2 cells) or Mock-c17.2 cells (c17.2 cells transfected with pcDNA3.1-Hygro vector) into the brains of 6-hydroxydopamine-lesioned PD model rats. From days 10 to 60 after grafting, double immunohistochemistry showed that IL-10 expression was detected in IL-10-c17.2 cells in vivo. Further immunohistochemistry analyses revealed that intracerebral cellular (ED1 and CD8) and humoral (C3 and IgM) immune responses were down-regulated in the rats treated with IL-10-c17.2 cells compared with controls treated with Mock-c17.2 cells. The reduction in ED1 immunostaining in the rats treated with IL-10-c17.2 cells remained significant until day 60 after transplantation. Our results suggest the potential application value of IL-10 in the transplantation treatment of PD.