RCAI-39, 41, 53, 100, 127 and 128, the analogues of KRN7000, activate mouse natural killer T cells to produce Th2-biased cytokines by their administration as liposomal particles

α-Galactosphingolipid analogues of KRN7000 with a sulfonamide (RCAI-39), a carbamate (RCAI-41), an α,α-difluorocarboxamide (RCAI-100) or an N-methylcarboxamide linkage (RCAI-127) instead of a carboxamide bond of KRN7000 were synthesized. Their bioactivities for mouse natural killer T cells were examined. Bioactivities of truncated analogues, OCH and RCAI-53, and β-galactosphingolipid (RCAI-128) were also examined. All of these glycosphingolipids induced Th2-biased cytokine production by their administration as liposomal particles. Among them, liposomes containing RCAI-127 induced the most potent Th2-biased response.