Suppression of eosinophilic airway inflammation by treatment with α-galactosylceramide

To clarify the essential role of NKT cells in allergy, we investigated the contribution of NKT cells to the pathogenesis of eosinophilic airway inflammation using α-galactosylceramide (α-GalCer), a selective ligand for NKT cells. Although continuous administration of α-GalCer during ovalbumin (OVA) sensitization increased OVA-specific IgE levels and worsened eosinophil inflammation, a single administration of α-GalCer at the time of OVA challenge completely prevented eosinophilic infiltration in wild-type mice. This inhibitory effect of α-GalCer was associated with a decrease in airway hyperresponsiveness, an increase in IFN-γ, and decreases in IL-4, IL-5 and IL-13 levels in the bronchoalveolar lavage fluids. Analysis of lung lymphocytes revealed that production of IFN-γ increased in NK cells, but not in T or NKT cells, following α-GalCer administration. Induction of vascular cell adhesion molecule-1 in the lungs of wild-type mice was also significantly attenuated by treatment with α-GalCer. These effects of α-GalCer were abrogated in Jα281–/– mice, which lack NKT cells, and in wild-type mice treated with anti-IFN-γ Ab. Hence, our data indicate that α-GalCer suppresses allergen-induced eosinophilic airway inflammation, possibly by inducing a Th1 bias that results in inhibition of eosinophil adhesion to the lung vessels. See accompanying commentary: http://dx.doi.org/10.1002/eji.200535425