Normal development and function of invariant natural killer T cells in mice with isoglobotrihexosylceramide (iGb3) deficiency
- Stefan Porubsky*,
- Anneliese O. Speak†,
- Bruno Luckow‡,
- Vincenzo Cerundolo§,
- Frances M. Platt†, and
- Hermann-Josef Gröne*,¶
- *Department of Cellular and Molecular Pathology, German Cancer Research Center, 69120 Heidelberg, Germany;
- †Department of Pharmacology, University of Oxford, Oxford OX1 3QT, United Kingdom;
- ‡Medical Policlinic of the University of Munich, Division of Clinical Biochemistry, 80336 Munich, Germany; and
- §Weatherall Institute of Molecular Medicine, Tumor Immunology Group, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom
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Edited by Peter Cresswell, Yale University School of Medicine, New Haven, CT, and approved February 8, 2007 (received for review December 15, 2006)
Abstract
CD1d-restricted natural killer T (NKT) cells, expressing the invariant T cell antigen receptor (TCR) chain encoded by Vα14-Jα18 gene segments in mice and Vα24-Jα18 in humans [invariant NKT (iNKT) cells], contribute to immunoregulatory processes, such as tolerance, host defense, and tumor surveillance. iNKT cells are positively selected in the thymus by CD1d molecules expressed by CD4+/CD8+ cortical thymocytes. However, the identity of the endogenous lipid(s) responsible for positive selection of iNKT cells remains unclear. One candidate lipid proposed to play a role in positive selection is isoglobotrihexosylceramide (iGb3). However, no direct evidence for its physiological role has been provided. Therefore, to directly investigate the role of iGb3 in iNKT cell selection, we have generated mice deficient in iGb3 synthase [iGb3S, also known as α1–3galactosyltransferase 2 (A3galt2)]. These mice developed, grew, and reproduced normally and exhibited no overt behavioral abnormalities. Consistent with the notion that iGb3 is synthesized only by iGb3S, lack of iGb3 in the dorsal root ganglia of iGb3S-deficient mice (iGb3S −/−), as compared with iGb3S +/− mice, was confirmed. iGb3S −/− mice showed normal numbers of iNKT cells in the thymus, spleen, and liver with selected TCR Vβ chains identical to controls. Upon administration of α-galactosylceramide, activation of iNKT and dendritic cells was similar in iGb3S −/− and iGb3S +/− mice, as measured by up-regulation of CD69 as well as intracellular IL-4 and IFN-γ in iNKT cells, up-regulation of CD86 on dendritic cells, and rise in serum concentrations of IL-4, IL-6, IL-10, IL-12p70, IFN-γ, TNF-α, and Ccl2/MCP-1. Our results strongly suggest that iGb3 is unlikely to be an endogenous CD1d lipid ligand determining thymic iNKT selection.
Footnotes
- ¶To whom correspondence should be addressed. E-mail: h.-j.groene{at}dkfz.de
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Author contributions: S.P., V.C., F.M.P., and H.-J.G. designed research; S.P., A.O.S., and B.L. performed research; S.P., A.O.S., and F.M.P. analyzed data; and S.P. and H.-J.G. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS direct submission.
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See Commentary on page 5713.
- Abbreviations:
- αGalCer,
- α-galactosylceramide;
- DC,
- dendritic cell;
- DRG,
- dorsal root ganglion;
- GSL,
- glycosphingolipid;
- iGb3,
- isoglobotrihexosylceramide;
- iGb3S,
- iGb3 synthase;
- iGb3S−/−,
- iGb3S-deficient;
- iGb4,
- isoglobotetrahexosylceramide;
- NKT,
- natural killer T;
- iNKT,
- invariant NKT;
- TCR,
- T cell antigen receptor.
- © 2007 by The National Academy of Sciences of the USA
