Enhancing effects of alpha-,beta-monoglycosylceramides on natural killer cell activity

We examined the in vitro and in vivo natural killer (NK) cell activity enhancing effects of alpha-, beta-galactosylceramide (GalCer) and alpha-, beta-glucosylceramide (GluCer) which have the same ceramide moiety, and of other alpha-, beta-GalCer having a different ceramide portion, and found that alpha-types show stronger enhancing effects than beta-types and the alpha-GalCer possesses the most potent activity among GalCers and GluCers having the same ceramide moiety. When the comparison of tumor growth inhibitory effects of alpha, beta-GalCer on mice subcutaneously inoculated with B16 cells was performed, the alpha-GalCer showed stronger suppressive activity than its beta-type, paralleling their enhancing effects on NK cell activity. These results suggest that the manner of combination between sugar and ceramide plays an important role in antitumor activity as well as enhancing effect on NK cell activity of GalCers.