Activation-induced NKT cell hyporesponsiveness protects from {alpha}-galactosylceramide hepatitis and is independent of active transregulatory factors

doi:10.1189/jlb.0607352

Activation-induced NKT cell hyporesponsiveness protects from ${alpha}$ -galactosylceramide hepatitis and is independent of active transregulatory factors

Markus Biburger^*^, and Gisa Tiegs^,^,1

^* Laboratory for Experimental Immunology and Immunotherapy, Nikolaus-Fiebiger-Center for Molecular Medicine, Medical Department III, University Hospital Erlangen, Germany;
Center of Internal Medicine, Division of Experimental Immunology and Hepatology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany; and
Institute of Experimental and Clinical Pharmacology and Toxicology, University of Erlangen-Nuremberg, Erlangen, Germany

¹Correspondence: Center of Internal Medicine, Division of Experimental Immunology and Hepatology, University Medical Centre Hamburg-Eppendorf, Hamburg, Martinistr. 52, 20246 Hamburg, Germany. E-mail: g.tiegs{at}uke.de

NK T (NKT) cells, unique lymphocytes expressing features ofNK and T lymphocytes, can specifically be activated with theglycolipid antigen ${alpha}$ -galactosylceramide ( ${alpha}$ -GalCer). In humansand mice, this activation provokes pronounced cytokine responses.In C57BL/6 mice, ${alpha}$ -GalCer injection additionally induces NKT-mediatedliver injury, representing a model for immune-mediated hepatitisin humans. However, a single ${alpha}$ -GalCer pretreatment of mice preventedNKT-mediated liver injury, cytokine responses (systemicallyand locally in the liver), and up-regulation of hepatocellularFas upon ${alpha}$ -GalCer rechallenge. As ${alpha}$ -GalCer is used as a NKT cell-activatingagent in clinical trials, an investigation of tolerance inductionappears crucial. We demonstrate that ${alpha}$ -GalCer tolerance doesnot depend on Kupffer cells, IL-10, Caspase-3-mediated apoptosis,or CD4⁺CD25⁺ T regulatory cells (T_regs), which are crucial inother models of immunological tolerance. Amending relevant,earlier approaches of others, we cocultivated highly purified,nontolerized and tolerized liver NKT cells ex vivo and couldconvincingly exclude the relevance of transdominant NKT T_regs.These results strongly suggest ${alpha}$ -GalCer-induced tolerance tobe exclusively caused by NKT cell intrinsic hyporesponsiveness.Tolerized mice showed specific diminishment of the intrahepaticCD4⁺ NKT cell subpopulation, with the CD4^– populationlargely unaffected, and revealed down-modulation of ${alpha}$ -GalCer-specificTCR and the NKT costimulator glucocorticoid-induced TNFR-relatedprotein on liver NKT cells, whereas inhibitory Ly49I was increased.In conclusion, ${alpha}$ -GalCer tolerance could serve as a model forthe frequently observed NKT cell hyporesponsiveness in tumorpatients and might help to develop strategies for their reactivation.Conversely, approaches to render NKT cells hyporesponsive mayconstitute new therapeutic strategies for diseases, where aberrantNKT cell activation is causally involved.

Key Words: lymphocytes • natural killer T cells • tolerance • liver immunology • anergy • animal models

Activation-induced NKT cell hyporesponsiveness protects from -galactosylceramide hepatitis and is independent of active transregulatory factors

Activation-induced NKT cell hyporesponsiveness protects from ${alpha}$ -galactosylceramide hepatitis and is independent of active transregulatory factors