alpha-GalCer is the first defined and most potent agonistic antigen of the T cell receptor of natural killer T cells. We have prepared a series of 1,2,3-triazole-containing alpha-GalCer analogues in which the lipid chain lengths have been incrementally varied. We found that this isosteric replacement of alpha-GalCer's amide moiety with triazole increases the IL-4 versus IFN-gamma bias of released cytokines. The stimulatory effect was influenced by the length of the attached chain. In particular, the long-chained triazole analogues have a comparable stimulatory effect on cytokine production as alpha-GalCer and exhibit a stronger Th2 cytokine response.

No abstract

We previously showed that although systemic administration of a-galactosylceramide (aGalCer) or agonistic anti-CD40 induced functional maturation of dendritic cells (DC) in mesenteric lymph nodes, only the former treatment succeeded in breaking the induction of oral tolerance. In this study, we looked for the essential factor responsible for the disruption of oral tolerance. We found that lamina propria (LP)-DC was responsible for the oral OVA presentation and that Peyer's patch was not essential for the induction of oral tolerance. Therefore, we investigated the role of LP-DC. Treatment with aGalCer but not with anti-CD40 induced the full maturation of LP-DC at an early time point. This functional activation of LP-DC was mediated by strong activation of NKT cells that reside abundantly in the small intestinal lamina propria (SI-LP) and interferon-c partially contributed to the LP-DC activation. LP-DC isolated from aGalCer-treated OVA-fed mice induced the differentiation of naïve CD4 1 T cells into Th1 and Th2 and was associated with the reduced Foxp3 1 population. In contrast, LP-DC isolated from anti-CD40-treated OVA-fed mice failed to generate Th cell differentiation but induced more Foxp3 1 CD4 1 T cells. Our results demonstrate that triggered by NKT cells in SI-LP, functional maturation of Ag-capturing DC from SI-LP is necessary for the abrogation of oral tolerance induction.

Our previous study revealed that a-galactosylceramide (a-GalCer) is a potent nasal vaccine adjuvant inducing both potent humoral and cellular immune responses and affording complete protection against viral infections and tumors. However, the antigen-presenting cells (APC) that are activated by NKT cells and thereby initiate the immune responses following intranasal coadministration of protein antigen and a-GalCer are poorly understood. We assessed here where antigen presentation occurs and which APC subset mediates the early stages of immune responses when protein antigen and a-GalCer are intranasally administered. We show that dendritic cells (DC), but not B cells, initiated the mucosal immune responses at mediastinal lymph nodes. Of the DC subsets, the CD8a -B220 -CD11c + DC subset played the most prominent role in the direct and cross-presentation of protein antigen to naive T cells and in triggering the naive T cells to differentiate into effector T cells. This might be mainly caused by a relatively larger population of CD1d high cells of CD8a -B220 -CD11c + DC subset than those of other DC subsets. These results indicate that CD8a -B220 -CD11c + DC is the principal subset becoming immunogenic after interaction with NKT cells and abrogating tolerance to intranasally administered protein antigen when a-GalCer is coadministered as a nasal vaccine adjuvant.