title: Chemical modification of iGb3 increases IFN-gamma production by hepatic NKT cells.
abstract: Isoglobotrihexosylceramide (iGb3) has been identified as an endogenous ligand recognized by NKT cells; however, it is a weak agonist compared to the exogenous alpha-galactosylceramide. Modification of the structure of iGb3 might improve its stimulatory activity. In this study, we assessed the stimulating activity of chemically-modified iGb3 analogues on murine hepatic NKT cells. We analyzed the percentage of IFN-gamma- or IL-4-producing cells in hepatic iNKT cell population and found that two chemically-modified iGb3 analogues, especially 4'''-dh-iGb3, induced significantly greater intracellular IFN-gamma+ NKT cells in liver by flow cytometry. In vivo experiments also showed that 4-HO-iGb3 and 4'''-dh-iGb3 are selectively strong inducer for rapid serum IFN-gamma production compared with unmodified iGb3. Comparing the structure of iGb3 and its two iGb3 analogues, 4-HO-iGb3 has an extra hydroxy group on C4, suggesting that the additional hydroxy group of phytosphingosine might augment the stability of the CD1d/glycoceramide complex forming and thereby possibly promote IFN-gamma producing. By further modifying the polysaccharide of glycolipid as did in 4'''-dh-iGb3, we found that 4'''-dh-iGb3 elicited more Th1-biased responses than iGb3 and 4-HO-iGb3. This modification might more strongly strengthen the affinity of the TCR/glycoceramide complex and ultimately polarize iNKT cells to release more Th1 cytokines. Our data suggests that a combination modification on both polysaccharide and sphingosine chain of iGb3 elicits preferential Th1-biased responses.
authors.affiliation: Institute of Basic Medicine, Shandong Academy of Medical Sciences, Jinan 250062, China.
authors.forename: Pingping
authors.initials: P
authors.lastname: Shang
authors.forename: Cai
authors.initials: C
authors.lastname: Zhang
authors.forename: Chengfeng
authors.initials: C
authors.lastname: Xia
authors.forename: Wenlan
authors.initials: W
authors.lastname: Chen
authors.forename: Qiuju
authors.initials: Q
authors.lastname: Han
authors.forename: Peng George
authors.initials: PG
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Tian
mesh_terms: D000276:Adjuvants, Immunologic; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000097:blood; D005434:Flow Cytometry; D005915:Globosides / Q000737:chemistry / Q000494:pharmacology*; D007371:Interferon-gamma / Q000096:biosynthesis*; D007694:Killer Cells, Natural / Q000187:drug effects / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D013329:Structure-Activity Relationship; D014281:Trihexosylceramides / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D000276:Adjuvants, Immunologic; D016207:Cytokines; D005915:Globosides; D014281:Trihexosylceramides; C514781:isoglobotrihexosylceramide; D007371:Interferon-gamma