Antibody-mediated T-cell reduction or increased levels of chimerism overcome resistance to cyclophosphamide-induced tolerance in NKT-deficient mice.
We reported that invariant NKT-cell knockout (iNKT KO) mice are resistant to the induction of intrathymic chimerism and clonal deletion in the cyclophosphamide (CP)-induced tolerance system (CPS). However, another report shows that clonal deletion with chimerism may be intact in iNKT KO recipients in a bone marrow transplantation model. We also reported that pretreatment with anti-Thy1.2 mAb, which reduces the number of T cells and iNKT cells, promotes allograft tolerance across H-2 barriers in the CPS. In this study, we evaluated the efficacy of T-cell depletion in the CPS, and the relationship between the role played by iNKT cells in central tolerance and mixed chimerism. BALB/c (H-2(d)) wild-type, or iNKT KO (Jalpha18(-/-)) mice were pretreated with 20-100 microg of anti-Thy1.2 mAb and given 10(8) donor DBA/2 (H-2(d)) spleen cells on Day 0, and 200 mg/kg CP on Day 2. Pretreatment with T-cell depletion resulted in higher levels of mixed chimerism, increased intrathymic clonal deletion of donor-reactive cells, and the induction of skin graft tolerance in iNKT KO recipients in CPS. This suggests that the high levels of mixed chimerism overcame the resistance to CP-induced tolerance in iNKT KO mice. Consistently, the enhancement of mixed chimerism by injection of tolerant donor spleen cells (SC) rendered iNKT KO recipients susceptible to CP-induced tolerance. These results suggest that iNKT-cell-mediated immunoregulation of central tolerance is evident at low levels of peripheral mixed chimerism in the CPS.
Onzuka
T
T
Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, Maidashi, Higashi-ku, Fukuoka, Japan.
Tomita
Y
Y
Okano
S
S
Shimizu
I
I
Yamada
H
H
Yoshikai
Y
Y
Tominaga
R
R
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000494:pharmacology; D003520:Cyclophosphamide / Q000494:pharmacology*; D005434:Flow Cytometry; D006085:Graft Survival / Q000276:immunology*; D007108:Immune Tolerance / Q000187:drug effects / Q000276:immunology*; D016130:Immunophenotyping; D007694:Killer Cells, Natural / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D018345:Mice, Knockout; D016038:Skin Transplantation / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000276:immunology; D018183:Transplantation Chimera / Q000276:immunology*
D000911:Antibodies, Monoclonal; D003520:Cyclophosphamide