Lysosomal storage disorders result from inherited defects in lysosomal proteins [10]. These disorders can be caused either by a primary defect in a catabolic Panobinostat enzyme (e.g. Tay-Sachs and Sandhoff disease) or a defect in a transporter, channel or regulatory protein (e.g. Niemann-Pick type C (NPC1) disease). Lysosomal storage caused by a deficient lysosomal enzyme has been shown to lead to reduced iNKT cells in murine models of Sandhoff disease [11, 12], Tay-Sachs disease [11], GM1 gangliosidosis

[11-13] and Fabry disease [14, 15]. In the NPC1 mouse the numbers of iNKT cells also are greatly reduced but this is associated with impaired late-endosome/lysosome fusion in addition to the lysosomal lipid storage [11, 16]. NPC disease can be caused by mutations in one of two genes NPC1 or NPC2 [17]. Dysfunction of the NPC1 protein leads to decreased lysosomal calcium content which accounts for the failure of endocytic vesicle fusion and the complex pattern of lipid storage observed [18]. With the differential trafficking of murine and human CD1d for iNKT-cell

ligand Daporinad nmr presentation ex vivo and the requirement of normal lysosomal CD1d trafficking/function for murine iNKT-cell development in vivo, we reasoned that examining iNKT cells in NPC patients would reveal whether the findings in the murine model extends to humans. It has been reported that iNKT cells are present at normal frequencies in the peripheral blood of Fabry disease patients [19] and are slightly increased in Gaucher disease patients [20]. Here, we have studied iNKT-cell frequencies and functional responses

in NPC1 disease patients and the ability of patient-derived EBV-B-cell lines to stimulate iNKT cells. In contrast to the murine model of NPC1, we found unchanged iNKT-cell frequencies in NPC1 patients. In addition, the functional response of NPC1 iNKT cells to stimulation was normal, as was the ability of NPC1 antigen presenting cells to present a variety of iNKT cells ligands to control iNKT cells. We analysed the frequency of iNKT Staurosporine cells in the peripheral blood of controls, NPC1 patients and NPC1 heterozygote carriers by flow cytometry (gating strategy, Supporting Information Fig. 1). As previously reported [21], the frequencies of iNKT cells are very low in normal human peripheral blood, typically in the range of 0.1–1% of total T cells (Fig. 1A). In contrast to the NPC1 mouse where iNKT cells are undetectable, iNKT cells could be identified and were present at normal frequencies in the peripheral blood of NPC1 patients and heterozygotes (Fig. 1A). This indicates that fusion of late endosomes and lysosomes is not required for the generation, delivery or loading of iNKT-cell selecting ligand(s) in the thymus or for their maintenance in the periphery.