Objective To observe the changes in the peripheral blood T lymphocyte subsets and the histomorphology of the transplanted tissues in the rabbits in the early stage after transplantation of the tissue engineered boneconstituted by the biologically-derived scaffold and to confirm the feasibility of the biologicallyderived materials as a scaffold in the bone tissue engineering. Methods Forty-eight healthy New Zealand rabbits (weight, 2.0-2.5 kg) with a 1-cm defect were equally and randomly divided into 4 groups: Groups A-D. The partial demineralized freeze-dried bone (PDFDB), the tissue engineered bone constructed by the osteoblasts derived from the lactant rabbit periosteum as a seeding cell, the xenogeneic cancellous bone undergoing the antigen self-digestion, partial demineralization and freeze-driedprocess as a scaffold, and the fresh xenogeneic allografting bone were respectively transplanted into the segmental defects of the rabbit radii in Groups A-D.To examine the effects of the 4 different materials, the flow cytometry was used to observe the changes in the T lymphocyte subsets in the rabbit peripheral blood at 1, 2, and 4 weeks after the operations and to examine the osteogenesis achieved by the 4 materials, the histological observations were also performed at 2, 4, 8, and 12 weeks after the operations. Results Two weeks after the tissue engineered bone transplantation in Group B, the osteoblasts and chondroblasts were found in the apertures of the scaffold, the new bone formation could be observed, the osteoclasts could be seen in the peripheral zone, and some of the netlike frameworks were destroyed and absorbed. Four weeks after the operation, the histological observation revealed that the osteocartilagionous callus turned into a woven bone. The peripheral blood T lymphocyte subsets of CD4+ and CD8+ were significantly greater in number 1-2 weeks after the operations and in Groups A and B than before the operations and in the other groups (.P lt;0.05)；4 weeks after the operations the T lymphocyte subset of CD4+ was only slightly greater in number than before the operations, but with no statistically significant difference (P gt;0.05). In Group C, the increase of the T lymphocyte subsets of CD4+ and CD8+ was not significant after the operation (P gt;0.05). The T lymphocyte subsets of CD4+ and CD8+ were significantly greater in number 1, 2 and 4 weeks after the operations and in Group D than before the operation and in the other groups (P lt;0.05). Conclusion The tissue engineered bone constructed by the partial demineralized freezedried bone as a scaffold does not cause a serious immunologic rejection in the early stage after the transplantation and does not affect its good ability to repair the bone defect. The biologicallyderived bone canbe used as a scaffold in the bone tissue engineering.

Citation： LI Yubiao,YANG Zhiming,QIN Tingwu,et al.. CHANGES IN PERIPHERAL BLOOD T LYMPHOCYTE SUBSETS OF RABBITS IN EARLY STAGE AFTER TRANSPLANTATION OF TISSUE ENGINEERED BONE CONSTITUTED BY BIOLOGICALLY-DERIVED SCAFFOLD. Chinese Journal of Reparative and Reconstructive Surgery, 2007, 21(2): 130-134. doi: Copy