Syntheses of biotinylated alpha-galactosylceramides and their effects on the immune system and CD1 molecules.

A representative alpha-galactosylceramide (alpha-GalCer), KRN7000, has strong immunostimulatory and antitumor activity. Recent studies demonstrated that KRN7000-pulsed antigen-presenting cells (APC) can activate natural killer T (NKT) cells, a novel T-cell lineage, and CD1d molecules on APC play an important role in the activation of NKT cells. However, it remains unclear whether alpha-GalCers actually bind to CD1d molecules. To address this question, we synthesized three kinds of biotinylated alpha-GalCer and a biotinylated beta-GalCer and found that the biotinylated alpha-GalCers significantly stimulate the proliferation of murine spleen cells, but the biotinylated beta-GalCer does not and that all biotinylated compounds bind to CD1d molecules.