Innate immune receptors for cross-presentation: The expanding role of NLRs

Background: Multiple sclerosis is the most common autoimmune disease of the central nervous system in young adults and histopathologically characterized by inflammation, demyelination and gliosis. It is considered as a CD4+ T cell-mediated disease, but also a disease-promoting role of the innate immune system has been proposed, based e.g. on the observation that innate immune receptors modulate disease severity of experimental autoimmune encephalomyelitis. Recent studies of our group provided first evidence for a key role of the innate immune LPS receptor (CD14) in pathophysiology of experimental autoimmune encephalomyelitis. CD14-deficient experimental autoimmune encephalomyelitis mice showed increased clinical symptoms and enhanced infiltration of monocytes and neutrophils in brain and spinal cord. Methods: In the current study, we further investigated the causes of the disease aggravation by CD14-deficiency and examined T cell activation, also focusing on the costimulatory molecules CTLA-4 and CD28, and T cell migration capacity over the blood brain barrier by FACS analysis, in vitro adhesion and transmigration assays. Results: In the results, we observed a significantly increased migration of CD14-deficient lymphocytes across an endothelial monolayer. In contrast, we did not see any differences in expression levels of TCR/CTLA-4 or TCR/CD28 and lymphocyte adhesion to endothelial cells from CD14-deficient compared to wildtype mice. Conclusion: The results demonstrate an important role of CD14 in migration of lymphocytes, and strengthen the importance of innate immune receptors in adaptive immune disorders, such as multiple sclerosis.

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Trem-2 modulation of gut microbiota is blunted during hepatotoxic injury and uncoupled from liver repair responses

10.1101/857078 ◽

2019 ◽

Author(s):

Inês Coelho ◽

Nádia Duarte ◽

Maria Paula Macedo ◽

Carlos Penha-Gonçalves

Keyword(s):

Gut Microbiota ◽

Liver Damage ◽

Liver Tissue ◽

Innate Immune ◽

Microbiota Composition ◽

Wild Type ◽

Immune Receptors ◽

Microbiota Diversity ◽

Gut Microbiota Composition

AbstractThe involvement of gut microbiota in liver disease has been addressed in the context of the “leaky gut hypothesis” postulating that dysbiosis allow microbial components to elicit liver inflammatory responses and hepatic tissue damage. Conversely, commensal gut microbiota acting on innate immune receptors protect against hepatotoxic insults. Given that mice deficient for the triggering receptor expressed on myeloid cells-2 (Trem-2) show increased vulnerability to experimental drug-induced hepatic damage we explored the possibility that Trem-2 is a modulator of gut microbiota composition.We found that microbiota composition in untreated Trem-2 KO mice differs from the wild-type showing overall decrease in microbiota diversity and increased representation of Verrucomicrobia. Interestingly, induction of liver damage with hepatotoxic drugs blunted this microbiota diversity difference and altered phyla composition with increased representation of Verrucomicrobia during acute hepatic injury and Proteobacteria during chronic challenge. Furthermore, co-housing experiments that homogenized microbiota diversity showed that the increased liver tissue vulnerability to hepatotoxic insults in Trem-2 KO mice was not dependent on microbiota composition. This work uncouples Trem-2 dependent alterations in gut commensal microbiota from Trem-2 pro-recovery effects in the damaged liver tissue. These findings support the possibility that unlinked actions of innate immune receptors contribute to disease association with microbiota alterations, particularly with the Verrucomicrobia phylum.ImportanceTrem-2 is a mammalian innate immunity receptor involved in development and resolution of tissue damage, namely in the brain and in the liver. Nevertheless, it is not known whether gut microbiota is contributing to these Trem-2 mediated phenotypes. We found that Trem-2 KO mice spontaneously display different gut microbiota composition as compared to wild-type mice, namely with increased abundance of the phylum Verrucomicrobia. Notably these differences do not impact the control of Trem-2 on liver tissue vulnerability to hepatotoxic insults. This work uncouples Trem-2 modulation of gut microbiota and the role of Trem-2 on responses to liver damage. This work brings new insights on role of innate immune receptors on the association of organic and systemic diseases with gut microbiota.

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Innate immune receptors in type 1 diabetes: the relationship to cell death-associated inflammation

Biochemical Society Transactions ◽

10.1042/bst20200131 ◽

2020 ◽

Vol 48 (3) ◽

pp. 1213-1225 ◽

Cited By ~ 1

Author(s):

Tae Kang Kim ◽

Myung-Shik Lee

Keyword(s):

Innate Immunity ◽

Type 1 Diabetes ◽

Inflammatory Responses ◽

Critical Role ◽

Innate Immune ◽

Therapeutic Modalities ◽

Immune Receptors ◽

Molecular Patterns

The importance of innate immunity in host defense and inflammatory responses has been clearly demonstrated after the discovery of innate immune receptors such as Toll-like receptors (TLRs) or Nucleotide-binding oligomerization domain-containing protein (Nod)-like receptors (NLRs). Innate immunity also plays a critical role in diverse pathological conditions including autoimmune diseases such as type 1 diabetes (T1D). In particular, the role of a variety of innate immune receptors in T1D has been demonstrated using mice with targeted disruption of such innate immune receptors. Here, we discuss recent findings showing the role of innate immunity in T1D that were obtained mostly from studies of genetic mouse models of innate immune receptors. In addition, the role of innate immune receptors involved in the pathogenesis of T1D in sensing death-associated molecular patterns (DAMPs) released from dead cells or pathogen-associated molecular patterns (PAMPs) will also be covered. Elucidation of the role of innate immune receptors in T1D and the nature of DAMPs sensed by such receptors may lead to the development of new therapeutic modalities against T1D.

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Advances in Understanding Activation and Function of the NLRC4 Inflammasome

International Journal of Molecular Sciences ◽

10.3390/ijms22031048 ◽

2021 ◽

Vol 22 (3) ◽

pp. 1048

Author(s):

Balamurugan Sundaram ◽

Thirumala-Devi Kanneganti

Keyword(s):

Immune Response ◽

Cell Death ◽

Innate Immune ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Immune Receptors ◽

Caspase 1 ◽

Cell Death Pathway ◽

Molecular Patterns

Innate immune receptors initiate a host immune response, or inflammatory response, upon detecting pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Among the innate immune receptors, nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) play a pivotal role in detecting cytosolic PAMPs and DAMPs. Some NLRs can form a multiprotein cytosolic complex known as the inflammasome. Inflammasome activation triggers caspase-1–mediated cleavage of the pore-forming protein gasdermin D (GSDMD), which drives a form of inflammatory cell death called pyroptosis. Parallelly, activated caspase-1 cleaves immature cytokines pro–IL-1β and pro–IL-18 into their active forms, which can be released via GSDMD membrane pores. The NLR family apoptosis inhibitory proteins (NAIP)-NLR family caspase-associated recruitment domain-containing protein 4 (NLRC4) inflammasome is important for mounting an immune response against Gram-negative bacteria. NLRC4 is activated through NAIPs sensing type 3 secretion system (T3SS) proteins from Gram-negative bacteria, such as Salmonella Typhimurium. Mutations in NAIPs and NLRC4 are linked to autoinflammatory disorders in humans. In this review, we highlight the role of the NAIP/NLRC4 inflammasome in host defense, autoinflammatory diseases, cancer, and cell death. We also discuss evidence pointing to a role of NLRC4 in PANoptosis, which was recently identified as a unique inflammatory programmed cell death pathway with important physiological relevance in a range of diseases. Improved understanding of the NLRC4 inflammasome and its potential roles in PANoptosis paves the way for identifying new therapeutic strategies to target disease.

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Role of Innate Immune Receptors in Paradoxical Caspofungin ActivityIn Vivoin Preclinical Aspergillosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05198-11 ◽

2012 ◽

Vol 56 (8) ◽

pp. 4268-4276 ◽

Cited By ~ 23

Author(s):

Silvia Moretti ◽

Silvia Bozza ◽

Carmen D'Angelo ◽

Andrea Casagrande ◽

Maria Agnese Della Fazia ◽

...

Keyword(s):

Invasive Aspergillosis ◽

Experimental Models ◽

Innate Immune ◽

Preclinical Models ◽

Immune Receptors ◽

Eagle Effect ◽

Dose Dependent

ABSTRACTThis study investigated the possible mechanisms underlying the paradoxical caspofungin activityin vivoin preclinical aspergillosis. We evaluated the activity of escalating doses of caspofunginin vivoin different preclinical models of invasive aspergillosis, including mice deficient for selected innate immune receptors. The therapeutic efficacy of caspofungin in experimental invasive aspergillosis was strictly dose dependent, being observed at doses of 0.1 and 1 mg/kg of body weight depending on the experimental models. Paradoxical increase in pulmonary fungal burden as well as inflammatory pathology was observed at the highest dose of caspofungin (5 mg/kg), occurred independently of the so-called Eagle effect and susceptibility to caspofunginin vitro, and was contingent upon the presence of TLR2, Dectin-1, and TLR9. Increased expression of Dectin-1 and TLR9 were observed upon exposure to caspofunginin vitroandin vivo. Together, these findings suggest that the net activity of caspofunginin vivois orchestrated by the activation, directly or indirectly, of multiple innate immune receptors.

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