title: Purified hematopoietic stem cell engraftment of rare niches corrects severe lymphoid deficiencies without host conditioning.
abstract: In the absence of irradiation or other cytoreductive conditioning, endogenous hematopoietic stem cells (HSCs) are thought to fill the unique niches within the bone marrow that allow maintenance of full hematopoietic potential and thus prevent productive engraftment of transplanted donor HSCs. By transplantation of purified exogenous HSCs into unconditioned congenic histocompatible strains of mice, we show that approximately 0.1-1.0% of these HSC niches are available for engraftment at any given point and find no evidence that endogenous HSCs can be displaced from the niches they occupy. We demonstrate that productive engraftment of HSCs within these empty niches is inhibited by host CD4+ T cells that recognize very subtle minor histocompatibility differences. Strikingly, transplantation of purified HSCs into a panel of severe combined immunodeficient (SCID) mice leads to a rapid and complete rescue of lymphoid deficiencies through engraftment of these very rare niches and expansion of donor lymphoid progenitors. We further demonstrate that transient antibody-mediated depletion of CD4+ T cells allows short-term HSC engraftment and regeneration of B cells in a mouse model of B(-) non-SCID. These experiments provide a general mechanism by which transplanted HSCs can correct hematopoietic deficiencies without any host conditioning or with only highly specific and transient lymphoablation.
authors.affiliation: Department of Pathology, Institute of Cancer and Stem Cell Biology and Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA. deepta@stanford.edu
authors.forename: Deepta
authors.initials: D
authors.lastname: Bhattacharya
authors.forename: Derrick J
authors.initials: DJ
authors.lastname: Rossi
authors.forename: David
authors.initials: D
authors.lastname: Bryder
authors.forename: Irving L
authors.initials: IL
authors.lastname: Weissman
mesh_terms: D000375:Aging / Q000276:immunology; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D006098:Granulocytes / Q000276:immunology; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000276:immunology; D006789:Host vs Graft Reaction; D007157:Immunologic Surveillance; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D016513:Mice, SCID; D016511:Severe Combined Immunodeficiency / Q000276:immunology* / Q000517:prevention & control; D013601:T-Lymphocytes / Q000276:immunology*; D018183:Transplantation Chimera
chemical_list: D004268:DNA-Binding Proteins; C499308:Rag2 protein, mouse