Innate and adaptive immune responses are tolerized in chimeras prepared with nonmyeloablative conditioning.
BACKGROUND
Mixed chimerism is an effective approach for tolerance induction in transplantation. Strategies to achieve mixed chimerism with relatively low toxicity have significantly expanded the clinical use of chimerism.


METHODS
Allogeneic bone marrow transplants were performed between B6 (H2(b)) and BALB/c (H2(d)) mice. Recipient B6 mice were nonmyeloablatively conditioned with anti-αβ-T-cell receptor, anti-CD154, or rapamycin alone or in different combinations. A total of 15 × 10(6) BALB/c bone marrow cells were transplanted after varying doses of cGy of total body irradiation.


RESULTS
Pretreatment of recipients with anti-CD154 and rapamycin with or without T-cell lymphodepletion reduced the total body irradiation requirement to 100 cGy for establishing stable mixed chimerism. The mixed chimeras accepted donor islet allografts long term. Lymphocytes from mixed chimeras did not respond to host or donor antigens, yet were reactive to major histocompatibility complex-disparate third-party alloantigens, demonstrating functional donor-specific T-cell tolerance. No antibodies against donor and host were detected in mixed chimeras, suggesting humoral tolerance. Mixed chimeras showed no cytotoxicity to donor cells, but a similar rapid killing rate for major histocompatibility complex disparate third-party B10.BR cells compared with T-cell-deficient and wild-type controls in in vivo cytotoxicity assays, suggesting donor-specific tolerance in the innate immune cells was achieved in mixed chimeras.


CONCLUSIONS
Mixed chimeras prepared with low-intensity nonmyeloablative conditioning exhibit systemic tolerance in innate immunity and tolerance in adaptive T- and B-cell immune responses.
Institute for Cellular Therapeutics, University of Louisville, Louisville, KY 40202-1760, USA.
Hong
H
Xu
Ziqiang
Z
Zhu
Yiming
Y
Huang
Larry D
LD
Bozulic
Lala-Rukh
LR
Hussain
Jun
J
Yan
Suzanne T
ST
Ildstad
D056704:Adaptive Immunity / Q000187:drug effects; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D016026:Bone Marrow Transplantation / Q000276:immunology*; D023201:CD40 Ligand / Q000276:immunology; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control; D006085:Graft Survival; D007108:Immune Tolerance / Q000187:drug effects; D056724:Immunity, Humoral; D007113:Immunity, Innate / Q000187:drug effects; D007166:Immunosuppressive Agents / Q000494:pharmacology; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D008212:Lymphocyte Depletion; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology; D020123:Sirolimus / Q000494:pharmacology; D016038:Skin Transplantation / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D013997:Time Factors; D018183:Transplantation Chimera / Q000276:immunology*; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous; D014916:Whole-Body Irradiation
D000911:Antibodies, Monoclonal; D007166:Immunosuppressive Agents; D016693:Receptors, Antigen, T-Cell, alpha-beta; D023201:CD40 Ligand; D020123:Sirolimus