Immunosuppressive effect of tacrolimus (FK-506): Bone xenografts in rabbits

We examined the immunomodulatory effect of the macrolide antibiotic FK-506 (tacrolimus) in bone xenograft transplantation. Full-thickness pieces of iliac bone from mongrel dogs were transplanted into the iliac bone of Japanese white rabbits. FK-506 at a dose of 1.6 mg/kg/day was injected into the rabbits for 10 days after transplantation. in the animals treated with FK-506, inflammatory cell infiltration was remarkably reduced and revascularization accompanied by new bone formation occurred in the grafts. At 4 months after the transplantation, the formation of new bone and of mature new bone marrow were observed. in a control group, inflammatory cell infiltration was marked around the graft from 2 weeks after the transplantation. Revascularization from the recipient site to the graft in the control group was poor and only a small amount of new bone had formed at 4 months. Our findings suggest that short-term administration of FK-506 has a beneficial effect on experimental xenograft bone transplantation.