Peripheral blood progenitor cell mobilization and leukapheresis in pigs

Background and Purpose: The pig is being investigated as an organ donor for humans. Induction of immunologic tolerance to pig tissues in primates woul d overcome the major immunologic barriers to xenotransplantation. A proven method of inducing tolerance to allografts is by the induction of mixed hem atopoietic chimerism by bone marrow transplantation. We are therefore inves tigating induction of mixed hematopoietic chimerism in the pig-to-baboon mo del. Methods: To obtain large numbers of pig hematopoietic cells, leukapheresis was used to collect blood cell products in miniature swine (n = 5) after pr ogenitor cell mobilization by use of a course of hematopoietic growth facto rs (cytokines), consisting of porcine interleukin 3, porcine stem cell fact or, and human granulocyte colony-stimulating factor. Results: Cytokine therapy and leukapheresis were well tolerated. Cytokine t herapy increased the total white blood cell count and allowed large numbers of leukocytes (60 x 10(10)) to be obtained by apheresis, of which approxim ately 0.1% were granulocyte-erythrocyte-monocyte-megakaryocyte colony-formi ng units (CFU-GEMMs), which are considered to be representative of hematopo ietic progenitors with multi-lineage potential. Conclusions: The combination of cytokine therapy and leukapheresis enables hematopoietic progenitor cells to be obtained safely from miniature swine.