Antibody‐Mediated T‐Cell Reduction or Increased Levels of Chimerism Overcome Resistance to Cyclophosphamide‐Induced Tolerance in NKT‐Deficient Mice

• Published in: Scandinavian journal of immunology 2010-08, Vol.72 (2), p.106-117
• Main Authors: Onzuka, T., Tomita, Y., Okano, S., Shimizu, I., Yamada, H., Yoshikai, Y., Tominaga, R.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - pharmacology; Cyclophosphamide - pharmacology; Flow Cytometry; Graft Survival - immunology; Immune Tolerance - drug effects; Immune Tolerance - immunology; Immunophenotyping; Killer Cells, Natural - immunology; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Knockout; Skin Transplantation - immunology; Spleen - cytology; Spleen - immunology; Transplantation Chimera - immunology
• ISSN: 0300-9475; 1365-3083
• DOI: 10.1111/j.1365-3083.2010.02417.x

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‐2d) wild‐type, or iNKT KO (Jα18−/−) mice were pretreated with 20–100 μg of anti‐Thy1.2 mAb and given 108 donor DBA/2 (H‐2d) 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.