Objective: This study examined the lymphocyte infiltration induced by neural stem cell grafts in the traumatized brain.
Methods: Sixty Sprague-Dawley rats were assigned randomly to transplantation (n = 30) or control (n = 30) groups, and each rat was subjected to brain contusion. The neural stem cells derived from Wistar rats were transplanted into the lesion of the transplantation group, and saline was injected instead into the controls. Local lymphocyte infiltration was studied using haematoxylin and eosin staining, immunohistochemistry and flow cytometry. The immunogenicity of neural stem cells was evaluated using MHC-I expression.
Results: About 6.57 +/- 0.44% of the neural stem cells expressed MHC-I. In the transplantation group, histological examination and immunohistochemistry revealed significant lymphocyte infiltration in the contusion. The ratio of CD4(+) lymphocytes to total cells in the lesions was 13.28 +/- 1.60% in the transplantation group and 0.41 +/- 0.12% in the controls (p < 0.01). Likewise, the ratio of CD8(+) lymphocytes to total cells was 5.11 +/- 1.03% in the transplantation group and 0.57 +/- 0.26% in the controls (p < 0.01).
Conclusions: Neural stem cells possess immunogenicity and can induce lymphocyte infiltration when transplanted into a traumatised brain. Our findings imply that immunosuppressive treatment is necessary following neural stem cell transplantation.