title: Microchimerism, donor dendritic cells, and alloimmune reactivity in recipients of Flt3 ligand-mobilized hemopoietic cells: modulation by tacrolimus.
abstract: Flt3 ligand (FL) is a potent hemopoietic growth factor that strikingly enhances stem cells and dendritic cells (DC) in vivo. We examined the impact of infusing FL-mobilized bone marrow (BM) cells on microchimerism and anti-donor reactivity in normal and tacrolimus-immunosuppressed, noncytoablated allogeneic recipients. BM from B10 (H2b) mice given FL (10 microg/day; days 0-8; FL-BM) contained a 7-fold higher incidence of potentially tolerogenic immature CD11c+ DC (CD40low, CD80low, CD86low, MHC IIlow) that induced alloantigen-specific T cell hyporesponsiveness in vitro. C3H (H2k) mice received 50 x 106 normal or FL-BM cells (day 0) and tacrolimus (2 mg/kg/day; days 0-12). On day 15, enhanced numbers of donor (IAb+) cells were detected in the thymi and spleens of FL-BM recipients. Tacrolimus markedly enhanced microchimerism, which declined as a function of time. Ex vivo splenocyte proliferative and CTL responses and Th1 cytokine (IFN-gamma) production in response to donor alloantigens were augmented by FL-BM infusion, but reduced by tacrolimus. Systemic infusion of purified FL-BM immature DC, equivalent in number to that in corresponding whole BM, confirmed their capacity to sensitize, rather than tolerize, recipient T cells in vivo. In vitro, tacrolimus suppressed GM-CSF-stimulated growth of myeloid DC from normal BM much more effectively than from FL-BM without affecting MHC class II or costimulatory molecule expression. Infusion of normal B10 BM cells at the time of transplant prolonged C3H heart allograft survival, whereas FL-BM cells did not. A therapeutic effect of tacrolimus on graft survival was observed in combination with normal, but not FL-BM cells. These findings suggest the need for alternative immunosuppressive strategies to calcineurin inhibition to enable the engraftment, survival, and immunomodulatory function of FL-enhanced, immature donor DC.
authors.affiliation: Thomas E. Starzl Transplantation Institute and Department of Surgery, University of Pittsburgh, PA 15213, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Morelli
authors.forename: M A
authors.initials: MA
authors.lastname: Antonysamy
authors.forename: T
authors.initials: T
authors.lastname: Takayama
authors.forename: H
authors.initials: H
authors.lastname: Hackstein
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: S
authors.initials: S
authors.lastname: Qian
authors.forename: N B
authors.initials: NB
authors.lastname: Zurowski
authors.forename: A W
authors.initials: AW
authors.lastname: Thomson
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D016026:Bone Marrow Transplantation / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002469:Cell Separation; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000637:transplantation*; D004334:Drug Administration Schedule; D004338:Drug Combinations; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D006085:Graft Survival / Q000187:drug effects; D016027:Heart Transplantation / Q000276:immunology; D019650:Hematopoietic Stem Cell Mobilization; D018380:Hematopoietic Stem Cell Transplantation; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D007262:Infusions, Intravenous; D007274:Injections, Intraperitoneal; D007519:Isoantigens / Q000276:immunology*; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion; D008221:Lymphoid Tissue / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000008:administration & dosage / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D011828:Radiation Chimera / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D016559:Tacrolimus / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000276:Adjuvants, Immunologic; D004338:Drug Combinations; D018984:Epitopes, T-Lymphocyte; D000949:Histocompatibility Antigens Class II; D007166:Immunosuppressive Agents; D007519:Isoantigens; D008024:Ligands; D008565:Membrane Proteins; C084881:flt3 ligand protein; D016559:Tacrolimus