Fractionated bone marrow transplantation in mongrel dogs.

For the purpose of inducing the specific tolerance by bone marrow trans plantation, the PHA non-responding cells out of the bone marrow cells were trans planted to mongrel dogs in order to avoid the acute graft-versus-host reaction after conditioning the animals with cyclophosphamide. And nine out of 13 mongrel dogs survived under the condition of successfully established chimerism. The mixed lymphocyte culture between donor and recipient showed no response after chimerism had been established, while chimera dogs responded normally against heterologous antigens. However, the phenomenon that the degree of donor cell occupancy decreased as time went by forced us to consider the existence of immunological reaction of recipient to donor cells.