Lipid extraction decreases the specific immunologic response to bone allografts in rabbits

The immunologic response against frozen bank bone is generally considered to have no clinical importance. In a previous study, the bone formation rate in frozen allografts was measured at standardized conditions in the Bone Harvest Chamber. By defatting frozen allografts, the bone formation rate increased. In the present study, the effect of defatting was further investigated, as the specific immunologic influence was excluded by using autografts. Pairs of grafts were frozen and one graft in each pair was defatted with chloroform/methanol. With these autografts there was no difference in bone formation rate between defatted and non-defatted implants, measured with 99mTc-MDP. Combined with the previous experiments, the results indicate that the increased bone formation rate in defatted allografts is caused by the removal of specific cell surface antigens. Thus, the immunologic reaction to bank bone can be diminished by defatting.