Activation of natural killer T cells by alpha-galactosylceramide in the presence of CD1d provides protection against colitis in mice

Background & Aims: CD1d is a major histocompatibility complex class I-like molecule that presents glycolipid antigens to a subset of natural killer (N K)1.1(+) T cells. These NK T cells exhibit important immunoregulatory funct ions in several autoimmune disease models. Methods: To investigate whether CD1d and NK T cells have a similar role in intestinal inflammation, the eff ects of the glycolipid, alpha-galactosylceramide (alpha-GalCer), on dextran sodium sulfate (DSS)-induced colitis were examined. Wild-type (WT), CD1d(- /-), and RAG(-/-) mice were examined for their response to either alpha-Gal Cer or the control analogue, alpha-mannosylceramide (alpha-ManCer). Results : WT mice, but not CD1d(-/-) and RAG-/- mice, receiving alpha-GalCer had a significant improvement in DSS-induced colitis based on body weight, bleedi ng, diarrhea, and survival when compared with those receiving alpha-ManCer. Elimination of NK T cells through antibody-mediated depletion resulted in a reduction of the effect of alpha-GalCer. Furthermore, adoptive transfer o f NK T cells preactivated by alpha-GalCer, but not alpha-ManCer, resulted i n diminished colitis. Using a fluorescent-labeled analogue of alpha-GalCer, confocal microscopy localized alpha-GalCer to the colonic surface epitheli um of WT but not CD1d(-/-) mice, indicating alpha-GalCer binds CD1d in the intestinal epithelium and may be functionally active at this site. Conclusi ons: These results show an important functional role for NK T cells, activa ted by alpha-GalCer in a CD1d-restricted manner, in regulating intestinal i nflammation.