Xenogeneic bone marrow transplantation .1. Cloning, expression, and species specificity of porcine IL-3 and granulocyte-macrophage colony-stimulating factor

Establishment of mixed bone marrow chimerism has been used to induce tolerance to solid organ transplants in several allograft and xenograft models. The species specificity displayed by some important hematopoietic cytokines potentially limits the efficacy of this approach in pig-to-primate models. In order to examine the role porcine-specific factors may play in the establishment of xenogeneic mixed bone marrow chimerism, we have cloned and heterologously expressed the genes encoding porcine IL-3 and granulocyte-macrophage colony-stimulating factor, two myeloid growth factors previously shown to have significant species specificity. The purified porcine factors are demonstrated here to be potent stimulators of porcine bone marrow cell proliferation, but to have little or no effect on primate cells. The species specificity of these factors is reciprocal, in that the corresponding human cytokines have little activity on porcine bone marrow cells.