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TLR9 activation induces normal neutrophil responses in a child with IRAK-4 deficiency: involvement of the direct PI3K pathway.

Abstract : Polymorphonuclear neutrophils (PMN) play a key role in innate immunity. Their activation and survival are tightly regulated by microbial products via pattern recognition receptors such as TLRs, which mediate recruitment of the IL-1R-associated kinase (IRAK) complex. We describe a new inherited IRAK-4 deficiency in a child with recurrent pyogenic bacterial infections. Analysis of the IRAK4 gene showed compound heterozygosity with two mutations: a missense mutation in the death domain of the protein (pArg12Cys) associated in cis-with a predicted benign variant (pArg391His); and a splice site mutation in intron 7 that led to the skipping of exon 7. A nontruncated IRAK-4 protein was detected by Western blotting. The patient's functional deficiency of IRAK-4 protein was confirmed by the absence of IRAK-1 phosphorylation after stimulation with all TLR agonists tested. The patient's PMNs showed strongly impaired responses (L-selectin and CD11b expression, oxidative burst, cytokine production, cell survival) to TLR agonists which engage TLR1/2, TLR2/6, TLR4, and TLR7/8; in contrast, the patient's PMN responses to CpG-DNA (TLR9) were normal, except for cytokine production. The surprisingly normal effect of CpG-DNA on PMN functions and apoptosis disappeared after pretreatment with PI3K inhibitors. Together, these results suggest the existence of an IRAK-4-independent TLR9-induced transduction pathway leading to PI3K activation. This alternative pathway may play a key role in PMN control of infections by microorganisms other than pyogenic bacteria in inherited IRAK-4 deficiency.
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Contributor : Carole Elbim <>
Submitted on : Tuesday, October 28, 2008 - 11:08:53 AM
Last modification on : Monday, November 23, 2020 - 3:48:04 PM
Long-term archiving on: : Sunday, April 11, 2010 - 11:01:57 PM


  • HAL Id : inserm-00179394, version 1
  • PUBMED : 17878374


Cyrille Hoarau, Bénédicte Gérard, Emmanuel Lescanne, Dominique Henry, Stéphanie François, et al.. TLR9 activation induces normal neutrophil responses in a child with IRAK-4 deficiency: involvement of the direct PI3K pathway.. Journal of Immunology, Publisher : Baltimore : Williams & Wilkins, c1950-. Latest Publisher : Bethesda, MD : American Association of Immunologists, 2007, 179 (7), pp.4754-65. ⟨inserm-00179394⟩



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