Structure-activity relationship and conformational analysis of monoglycosylceramides on the syngeneic mixed leukocyte...

We examined effects of alpha-, beta-galactosylceramides (CalCers) and alpha-, beta-glucosylceramides (GlcCers) on the syngeneic mixed leukocyte reaction (MLR) using spleen cells (responder cells) and dendritic cells (DC, stimulator cells). The DC pretreated with these alpha-monoglycosylceramides markedly stimulated the proliferation of spleen cells, in contrast to the little stimulatory effects produced by the DC pretreated with the corresponding beta-anomers. In addition, when we compared the effects of alpha-GalCer derivatives on the syngeneic MLR, it appeared that the 2"- and 3-hydroxyl groups in alpha-GalCers play a critical role in their stimulation of the MLR response. Based on these results, we performed a computer-aided molecular modeling study, and found that the orientations of the 2"-, 4"- and 3-hydroxyl groups common to alpha-GalCer and alpha-GlcCer are not accessible to those of inactive monoglycosyleeramides such as beta-GalCer. These results suggest that there might be a receptor-like site for alpha-monoglycosylceramides on the cells which are involved in the MLR response.