title: Future strategies for tolerance induction: a comparative study between hematopoietic stem cells and macrophages.
abstract: So far, clinical benefit of hematopoietic stem cell induced donor-specific tolerance across major histocompatibility complex (MHC) barriers was hampered by either graft rejection or graft-versus-host disease. An alternative approach focuses on the use of donor-derived cells that bear an inherent mechanism to circumvent allospecific rejection upon injection into non-immunosuppressed hosts. Using a myeloablative conditioning model in the rat, full donor chimeric recipients were generated and their potential to induce long-term cardiac allograft survival was compared with the fate of grafts transferred to non-immunosuppressed host rats pretreated with donor-macrophages derived from the peritoneal cavity in the LEW to DA inbred strain combination. The induction of full multilineage long-term donor-chimerism (> 150 days) after initial host conditioning using two doses of cyclophosphamide and one shot of busulphan prevented acute graft rejection, whereas non-chimeric animals experienced acute and complete rejection. Conversely, vigorous T-cell depletion is required to protect conditioned animals from lethal graft-versus-host disease. Instead, the use of donor intraperitoneal macrophages achieved a state of transient chimerism and subsequent long-term graft survival in fully immunocompetent rats without the need of lethal conditioning regimens. In conclusion, the complex immunologic interactions, observed after allogeneic bone marrow transplantation as a means to induce donor chimerism, and subsequent long-term graft acceptance can be avoided if appropriate cell populations can be identified that, by themselves, induce a transient state of donor chimerism prevailing long enough to deviate allospecific immune responses, as outlined in this study.
mesh_terms: D000818:Animals; D016465:Bone Marrow Purging; D016026:Bone Marrow Transplantation / Q000276:immunology*; D018801:CD2 Antigens / Q000502:physiology; D004622:Embryo, Mammalian / Q000276:immunology; D005260:Female; D016027:Heart Transplantation / Q000276:immunology*; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D007108:Immune Tolerance; D008264:Macrophages / Q000502:physiology*; D008297:Male; D010587:Phagocytosis; D051381:Rats; D011917:Rats, Inbred Lew; D018183:Transplantation Chimera / Q000276:immunology*
chemical_list: D018801:CD2 Antigens