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 t olerance to solid organ transplants in several allograft and xenograft models. The species specificity displayed by some important hematopoi etic cytokines potentially limits the efficacy of this approach in pig -to-primate models. In order to examine the role porcine-specific fact ors may play in the establishment of xenogeneic mixed bone marrow chim erism, 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 s pecificity. The purified porcine factors are demonstrated here to be p otent stimulators of porcine bone marrow cell proliferation, but to ha ve little or no effect on primate cells. The species specificity of th ese factors is reciprocal, in that the corresponding human cytokines h ave little activity on porcine bone marrow cells.