title: Mixed chimerism induced without lethal conditioning prevents T cell- and anti-Gal alpha 1,3Gal-mediated graft rejection.
abstract: Gal alpha 1,3Gal-reactive (Gal-reactive) antibodies are a major impediment to pig-to-human xenotransplantation. We investigated the potential to induce tolerance of anti-Gal-producing cells and prevent rejection of vascularized grafts in the combination of alpha 1,3-galactosyltransferase wild-type (GalT(+/+)) and deficient (GalT(-/-)) mice. Allogeneic (H-2 mismatched) GalT(+/+) bone marrow transplantation (BMT) to GalT(-/-) mice conditioned with a nonmyeloablative regimen, consisting of depleting CD4 and CD8 mAb's and 3 Gy whole-body irradiation and 7 Gy thymic irradiation, led to lasting multilineage H-2(bxd) GalT(+/+) + H-2(d) GalT(-/-) mixed chimerism. Induction of mixed chimerism was associated with a rapid reduction of serum anti-Gal naturally occurring antibody levels. Anti-Gal-producing cells were undetectable by 2 weeks after BMT, suggesting that anti-Gal-producing cells preexisting at the time of BMT are rapidly tolerized. Even after immunization with Gal-bearing xenogeneic cells, mixed chimeras were devoid of anti-Gal-producing cells and permanently accepted donor-type GalT(+/+) heart grafts (>150 days), whereas non-BMT control animals rejected these hearts within 1-7 days. B cells bearing receptors for Gal were completely absent from the spleens of mixed chimeras, suggesting that clonal deletion and/or receptor editing may maintain B-cell tolerance to Gal. These findings demonstrate the principle that induction of mixed hematopoietic chimerism with a potentially relevant nonmyeloablative regimen can simultaneously lead to tolerance among both T cells and Gal-reactive B cells, thus preventing vascularized xenograft rejection.
authors.affiliation: Transplantation Biology Research Center, Surgical Service, Massachusetts General Hospital/Harvard Medical School, Boston 02129, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ohdan
authors.forename: Y G
authors.initials: YG
authors.lastname: Yang
authors.forename: A
authors.initials: A
authors.lastname: Shimizu
authors.forename: K G
authors.initials: KG
authors.lastname: Swenson
authors.forename: M
authors.initials: M
authors.lastname: Sykes
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology; D016026:Bone Marrow Transplantation / Q000276:immunology*; D019070:Cell Lineage / Q000235:genetics / Q000276:immunology; D004187:Disaccharides / Q000276:immunology*; D005700:Galactosyltransferases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D006084:Graft Rejection / Q000235:genetics* / Q000276:immunology / Q000517:prevention & control*; D006085:Graft Survival / Q000235:genetics / Q000276:immunology; D016027:Heart Transplantation / Q000276:immunology*; D007108:Immune Tolerance / Q000235:genetics; D007518:Isoantibodies / Q000096:biosynthesis; D008231:Lymphopenia / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D016513:Mice, SCID; D011828:Radiation Chimera; D013154:Spleen / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D019172:Transplantation Conditioning / Q000379:methods*
chemical_list: D004187:Disaccharides; D007518:Isoantibodies; C055075:galactosyl-(1-3)galactose; D005700:Galactosyltransferases