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Immune complexes inhibit IL-1 secretion and inflammasome activation.

ABSTRACT: IgG immune complexes have been shown to modify immune responses driven by APCs in either a pro- or anti-inflammatory direction depending upon the context of stimulation. However, the ability of immune complexes to modulate the inflammasome-dependent innate immune response is unknown. In this study, we show that IgG immune complexes suppress IL-1? and IL-1? secretion through inhibition of inflammasome activation. The mechanism by which this inhibition occurs is via immune complex ligation of activating Fc?Rs, resulting in prevention of both activation and assembly of the inflammasome complex in response to nucleotide-binding domain leucine-rich repeat (NLR) P3, NLRC4, or AIM2 agonists. In vivo, administration of Ag in the form of an immune complex during priming of the immune response inhibited resultant adaptive immune responses in an NLRP3-dependent model of allergic airway disease. Our data reveal an unexpected mechanism regulating CD4(+) T cell differentiation, by which immune complexes suppress inflammasome activation and the generation of IL-1? and IL-1? from APCs, which are critical for the Ag-driven differentiation of CD4(+) T cells.

SUBMITTER: Janczy JR

PROVIDER: S-EPMC4225162 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Immune complexes inhibit IL-1 secretion and inflammasome activation.

Janczy John R JR Ciraci Ceren C Haasken Stefanie S Iwakura Yoichiro Y Olivier Alicia K AK Cassel Suzanne L SL Sutterwala Fayyaz S FS

Journal of immunology (Baltimore, Md. : 1950) 20141015 10

IgG immune complexes have been shown to modify immune responses driven by APCs in either a pro- or anti-inflammatory direction depending upon the context of stimulation. However, the ability of immune complexes to modulate the inflammasome-dependent innate immune response is unknown. In this study, we show that IgG immune complexes suppress IL-1α and IL-1β secretion through inhibition of inflammasome activation. The mechanism by which this inhibition occurs is via immune complex ligation of acti ...[more]

PMID: 25320279

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Project description:Cryptococcus neoformans is an encapsulated yeast that causes disease mainly in immunosuppressed hosts. It is considered a facultative intracellular pathogen because of its capacity to survive and replicate inside phagocytes, especially macrophages. This ability is heavily dependent on various virulence factors, particularly the glucuronoxylomannan (GXM) component of the polysaccharide capsule. Inflammasome activation in phagocytes is usually protective against fungal infections, including cryptococcosis. Nevertheless, recognition of C. neoformans by inflammasome receptors requires specific changes in morphology or the opsonization of the yeast, impairing proper inflammasome function. In this context, we analyzed the impact of molecules secreted by C. neoformans B3501 strain and its acapsular mutant Δcap67 in inflammasome activation in an in vitro model. Our results showed that conditioned media derived from B3501 was capable of inhibiting inflammasome-dependent events (i.e., IL-1β secretion and LDH release via pyroptosis) more strongly than conditioned media from Δcap67, regardless of GXM presence. We also demonstrated that macrophages treated with conditioned media were less responsive against infection with the virulent strain H99, exhibiting lower rates of phagocytosis, increased fungal burdens, and enhanced vomocytosis. Moreover, we showed that the aromatic metabolite DL-Indole-3-lactic acid (ILA) and DL-p-Hydroxyphenyllactic acid (HPLA) were present in B3501's conditioned media and that ILA alone or with HPLA is involved in the regulation of inflammasome activation by C. neoformans. These results were confirmed by in vivo experiments, where exposure to conditioned media led to higher fungal burdens in Acanthamoeba castellanii culture as well as in higher fungal loads in the lungs of infected mice. Overall, the results presented show that conditioned media from a wild-type strain can inhibit a vital recognition pathway and subsequent fungicidal functions of macrophages, contributing to fungal survival in vitro and in vivo and suggesting that secretion of aromatic metabolites, such as ILA, during cryptococcal infections fundamentally impacts pathogenesis.

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Immune complexes inhibit IL-1 secretion and inflammasome activation.

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Immune complexes inhibit IL-1 secretion and inflammasome activation.

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