title: Enhanced gamma interferon production through activation of Valpha14(+) natural killer T cells by alpha-galactosylceramide in interleukin-18-deficient mice with systemic cryptococcosis.
abstract: We showed recently that activation of Valpha14(+) natural killer T cells (NKT cells) by alpha-galactosylceramide (alpha-GalCer) resulted in increased gamma interferon (IFN-gamma) production and host resistance to intravenous infection with Cryptococcus neoformans. In other studies, interleukin-18 (IL-18) activated NKT cells in collaboration with IL-12, suggesting the possible contribution of this cytokine to alpha-GalCer-induced IFN-gamma synthesis. Here we examined the role of IL-18 in alpha-GalCer-induced Th1 response by using IL-18KO mice with this infection. In these mice, levels of IFN-gamma in serum and its synthesis in vitro by spleen cells stimulated with live organisms were not reduced, but rather enhanced, compared to those in wild-type (WT) mice, while such production was completely absent in IL-12KO mice. The enhanced production of IFN-gamma correlated with increased IL-12 synthesis but not with reduced production of IL-4, which was rather increased. IFN-gamma synthesis in IL-18KO mice was abolished by neutralizing anti-IL-12 antibody and significantly inhibited by neutralization of endogenous IL-4 with a specific monoclonal antibody. In addition, administration of recombinant IL-4 significantly enhanced the production of IFN-gamma in WT mice. Finally, the enhanced production of IFN-gamma in IL-18KO mice correlated with increased host defense against cryptococcal infection, as indicated by enhancement in alpha-GalCer-related clearance of microorganisms. Our results indicated that in IL-18KO mice, IFN-gamma synthesis was enhanced through overproduction of IL-12 and IL-4 after intravenous infection with C. neoformans and a ligand-specific activation of Valpha14(+) NKT cells.
authors.affiliation: First Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan. kawakami@med.u-ryukyu.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Kawakami
authors.forename: Y
authors.initials: Y
authors.lastname: Kinjo
authors.forename: S
authors.initials: S
authors.lastname: Yara
authors.forename: K
authors.initials: K
authors.lastname: Uezu
authors.forename: Y
authors.initials: Y
authors.lastname: Koguchi
authors.forename: M
authors.initials: M
authors.lastname: Tohyama
authors.forename: M
authors.initials: M
authors.lastname: Azuma
authors.forename: K
authors.initials: K
authors.lastname: Takeda
authors.forename: S
authors.initials: S
authors.lastname: Akira
authors.forename: A
authors.initials: A
authors.lastname: Saito
mesh_terms: D000818:Animals; D003453:Cryptococcosis / Q000097:blood / Q000276:immunology*; D003455:Cryptococcus neoformans / Q000276:immunology; D005260:Female; D005699:Galactosylceramides / Q000494:pharmacology*; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000097:blood; D018664:Interleukin-12 / Q000235:genetics / Q000502:physiology; D020382:Interleukin-18 / Q000235:genetics / Q000502:physiology*; D015847:Interleukin-4 / Q000096:biosynthesis; D007694:Killer Cells, Natural / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D018417:Th1 Cells / Q000166:cytology
chemical_list: D005699:Galactosylceramides; D020382:Interleukin-18; D016693:Receptors, Antigen, T-Cell, alpha-beta; D018664:Interleukin-12; D015847:Interleukin-4; D007371:Interferon-gamma