Bone grafts in T-cell deficient rats

Revascularization, new bone formation, and resorption of fresh syngeneic and allogeneic cancellous bone that were transplanted to an intramuscular pouch have been studied in athymic and normal rats. Revascularization was evaluated with radioactive microspheres; formation of new bone was assessed with 85Sr incorporation; and resorption was measured by the graft weight reduction. Animals were killed 2, 6, or 12 weeks after transplantation. The circulation and bone formation in allogeneic grafts were greatly impaired in normal rats as compared with the athymic group and the syngeneic grafts. The allografts in normal rats had a smaller weight reduction than the allografts in athymic rats, suggesting impaired resorption. We conclude that the T-lymphocyte system is at least partly responsible for the difference between syngeneic and allogeneic bone grafts, and that the thymus-dependent primary rejection mechanism probably is important for the vitality of allogeneic bone grafts.