title: Long-term mixed chimerism after immunologic conditioning and MHC-mismatched stem-cell transplantation is dependent on NK-cell tolerance.
abstract: T-cell tolerance is mandatory for major histocompatibility complex (MHC)-mismatched stem-cell transplantation without cytoreduction. Here, we used a cytotoxicity assay based on the infusion of differentially carboxyfluorescein succinimidyl ester (CFSE)-labeled syngeneic and donor splenocytes to determine the survival of donor cells in vivo. In vivo cytotoxicity data showed that treatment with anti-CD40 ligand monoclonal antibody in combination with a low dose of MHC-mismatched bone marrow cells was sufficient to induce T-cell tolerance. However, CFSE-labeled donor cells were still eliminated. A similar elimination pattern was observed in T-cell and natural killer T-cell (NKT-cell)-deficient mice, suggesting the involvement of natural killer (NK) cells. Indeed, in vivo NK-cell depletion resulted in a prolonged survival of CFSE-labeled donor cells, confirming the role of NK cells in this process. Transplantation of a megadose of MHC-mismatched bone marrow cells was required for a complete survival of CFSE-labeled donor cells. This NK-cell tolerance was donor specific and was associated with mixed chimerism. Additional NK-cell depletion significantly enhanced engraftment and allowed long-term chimerism after transplantation of a relatively low dose of donor bone marrow cells. These data demonstrate the importance of NK cells in the rejection of MHC-mismatched hematopoietic cells and may explain the high numbers of bone marrow cells required for transplantation over MHC barriers.
authors.affiliation: Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands.
authors.forename: Geert
authors.initials: G
authors.lastname: Westerhuis
authors.forename: Wendy G E
authors.initials: WG
authors.lastname: Maas
authors.forename: Roel
authors.initials: R
authors.lastname: Willemze
authors.forename: René E M
authors.initials: RE
authors.lastname: Toes
authors.forename: Willem E
authors.initials: WE
authors.lastname: Fibbe
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D023201:CD40 Ligand; D003602:Cytotoxicity, Immunologic; D006085:Graft Survival; D018380:Hematopoietic Stem Cell Transplantation / Q000379:methods*; D006648:Histocompatibility; D006649:Histocompatibility Antigens; D007108:Immune Tolerance / Q000187:drug effects / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018183:Transplantation Chimera; D019172:Transplantation Conditioning / Q000379:methods*; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; D006649:Histocompatibility Antigens; D023201:CD40 Ligand