Spontaneous focal activation of invariant natural killer T (iNKT) cells in mouse liver and kidney.
BACKGROUND
Invariant natural killer T (iNKT) cells differ from other T cells by their hyperactive effector T-cell status, in addition to the expression of NK lineage receptors and semi-invariant T-cell receptors. It is generally agreed that the immune phenotype of iNKT cells is maintained by repeated activation in peripheral tissues although no explicit evidence for such iNKT cell activity in vivo has so far been reported.


RESULTS
We used an interferon (IFN)-γ-inducible cytoplasmic protein, Irga6, as a histological marker for local IFN-γ production. Irga6 was intensely expressed in small foci of liver parenchymal cells and kidney tubular epithelium. Focal Irga6 expression was unaffected by germ-free status or loss of TLR signalling and was totally dependent on IFN-γ secreted by T cells in the centres of expression foci. These were shown to be iNKT cells by diagnostic T cell receptor usage and their activity was lost in both CD1 d and Jα-deficient mice.


CONCLUSIONS
This is the first report that supplies direct evidence for explicit activation events of NKT cells in vivo and raises issues about the triggering mechanism and consequences for immune functions in liver and kidney.
Institute for Genetics, University of Cologne, Zuelpicher Strasse 47a, 50674 Cologne, Germany.
Jia
J
Zeng
Jonathan C
JC
Howard
D000818:Animals; D004848:Epithelium / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005856:Germ-Free Life; D007371:Interferon-gamma / Q000378:metabolism*; D007684:Kidney Tubules / Q000166:cytology* / Q000378:metabolism; D008099:Liver / Q000166:cytology* / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D055611:Natural Killer T-Cells / Q000166:cytology / Q000276:immunology*; D016133:Polymerase Chain Reaction
D007371:Interferon-gamma; D020558:GTP Phosphohydrolases; C491070:Iigp1 protein, mouse