title: Innate and cytokine-driven signals, rather than microbial antigens, dominate in natural killer T cell activation during microbial infection.
abstract: Invariant natural killer T cells (iNKT cells) are critical for host defense against a variety of microbial pathogens. However, the central question of how iNKT cells are activated by microbes has not been fully explained. The example of adaptive MHC-restricted T cells, studies using synthetic pharmacological α-galactosylceramides, and the recent discovery of microbial iNKT cell ligands have all suggested that recognition of foreign lipid antigens is the main driver for iNKT cell activation during infection. However, when we compared the role of microbial antigens versus innate cytokine-driven mechanisms, we found that iNKT cell interferon-γ production after in vitro stimulation or infection with diverse bacteria overwhelmingly depended on toll-like receptor-driven IL-12. Importantly, activation of iNKT cells in vivo during infection with Sphingomonas yanoikuyae or Streptococcus pneumoniae, pathogens which are known to express iNKT cell antigens and which require iNKT cells for effective protection, also predominantly depended on IL-12. Constitutive expression of high levels of IL-12 receptor by iNKT cells enabled instant IL-12-induced STAT4 activation, demonstrating that among T cells, iNKT cells are uniquely equipped for immediate, cytokine-driven activation. These findings reveal that innate and cytokine-driven signals, rather than cognate microbial antigen, dominate in iNKT cell activation during microbial infections.
authors.affiliation: Department of Pathology, Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA. mbrigl@rics.bwh.harvard.edu
authors.forename: Manfred
authors.initials: M
authors.lastname: Brigl
authors.forename: Raju V V
authors.initials: RV
authors.lastname: Tatituri
authors.forename: Gerald F M
authors.initials: GF
authors.lastname: Watts
authors.forename: Veemal
authors.initials: V
authors.lastname: Bhowruth
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Leadbetter
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Barton
authors.forename: Nadia R
authors.initials: NR
authors.lastname: Cohen
authors.forename: Fong-Fu
authors.initials: FF
authors.lastname: Hsu
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.forename: Michael B
authors.initials: MB
authors.lastname: Brenner
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000378:metabolism*; D016207:Cytokines / Q000378:metabolism*; D005260:Female; D005699:Galactosylceramides / Q000737:chemistry; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D008024:Ligands; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D055611:Natural Killer T-Cells / Q000378:metabolism / Q000382:microbiology*; D010766:Phosphorylation; D050797:STAT4 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D020578:Sphingomonas / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000378:metabolism
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; D005699:Galactosylceramides; D008024:Ligands; D050797:STAT4 Transcription Factor; C493154:alpha-galactosylceramide; D018664:Interleukin-12; D007371:Interferon-gamma