An irradiation-free nonmyeloablative bone marrow transplantation model: importance of the balance between donor T-cell number and the intensity of conditioning.
BACKGROUND
Animal allogeneic bone marrow transplantation (BMT) models with nonmyeloablative conditioning regimens have so far required irradiation or antibodies in addition to immunosuppressive drugs for engraftment. Moreover, although it is known that the balance between donor T-cell number and the dose of immunosuppressive drugs would be critical for engraftment, it has not been experimentally clarified in a nonmyeloablative regimen.


METHODS
We used C57BL/6 mice as donors and DBA/2 mice as recipients with a nonmyeloablative regimen including fludarabine (Flu) and cyclophosphamide (CPA) without irradiation or antibodies. To determine the adequate doses, we injected recipients with various doses of Flu and CPA, and 2x10 bone marrow cells (BMC) and 5x10 splenocytes (SC). Furthermore, using T-cell-depleted BMC and enriched T cells, we investigated the balance between donor T-cell number and the dose of Flu.


RESULTS
Doses of Flu at 150 mg/kg/dayx6 and CPA at 150 mg/kg/dayx2 were most appropriate for engraftment with low mortality. All mice appropriately pretreated and transplanted with both BMC and SC exhibited complete donor chimeras. Donor cell engraftment was not enhanced by any increase of BMC transplanted, and dose escalation of donor T cells but not BMC led to the reduction of Flu dose required for engraftment of donor cells.


CONCLUSIONS
We have established a murine nonmyeloablative BMT model in a fully MHC-mismatched combination for donor cell engraftment with complete donor chimerism. Simultaneously, we have quantitatively demonstrated that the balance between donor T-cell number and the dose of immunosuppressive drugs is critical for stable engraftment.
Kuwatani
Masaki
M
Pharmacology Division, National Cancer Center Research Institute, Tokyo, and Department of Gastroenterology, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
Ikarashi
Yoshinori
Y
Mineishi
Shin
S
Asaka
Masahiro
M
Wakasugi
Hiro
H
D000818:Animals; D001854:Bone Marrow Cells / Q000502:physiology; D016026:Bone Marrow Transplantation / Q000009:adverse effects; D017690:Cell Transplantation; D003520:Cyclophosphamide / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006086:Graft vs Host Disease / Q000209:etiology; D018655:Lymphocyte Count; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000166:cytology*; D014019:Tissue Donors; D018183:Transplantation Chimera; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous; D014740:Vidarabine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology
D003520:Cyclophosphamide; D014740:Vidarabine; C024352:fludarabine