GSL-1 is structurally similar to PBS-57 and a-galactosylceramide. Through a collaboration with Dr. Paul Savage at Brigham Young University, the NIH Tetramer Facility is providing purified GSL-1. Purified GSL-1 ligand may also be obtained for stimulation of NK T cells in vitro or for in vivo animal studies. (The material may not be used in humans.) GSL-1 is dissolved in a Tween/sucrose/histidine buffer, sterile-filtered, placed in autoclaved vials, and lyophilized. The resulting powder can be reconstituted in water at a final concentration of 0.2 mg/mL.