The effects of NOD-like receptors on adaptive immune responses

It has long been appreciated that cues from the innate immune system orchestrate downstream adaptive immune responses. Although previous work has focused on the roles of Toll-like receptors in this regard, relatively little is known about how Nod-like receptors instruct adaptive immunity. Here we review the functions of different members of the Nod-like receptor family in orchestrating effector and anamnestic adaptive immune responses. In particular, we address the ways in which inflammasome and non-inflammasome members of this family affect adaptive immunity under various infectious and environmental contexts. Furthermore, we identify several key mechanistic questions that studies in this field have left unaddressed. Our aim is to provide a framework through which immunologists in the adaptive immune field may view their questions through an innate-immune lens and vice-versa.

A173 ELUCIDATING THE EFFECTS OF NOD2-MEDIATED SIGNALLING ON INTESTINAL RESIDENT-MEMORY T-CELL FORMATION AND FUNCTION

Background

Aberrant resident memory T-cell (TRM) responses have been associated with increased intestinal inflammation and Crohn’s disease (CD) pathology in humans. Intestinal TRM cells are not only important for maintaining the integrity of the intestinal epithelial barrier, but also for the rapid clearance of pathogens in the intestine during infection. Understanding the signals received by the intestinal immune system to generate TRM responses is paramount to elucidating treatments for CD. Genetic mutations in NOD2 are associated with the highest risk of CD development. As a host intracellular sensor of bacterial peptidoglycan, NOD2 is critical for initiating both innate and adaptive immune responses. Furthermore, work from our lab as well as those of our collaborators suggest that NOD2 deficiency reduces systemic memory B and T-cell responses. However, the role of NOD2 in establishing memory T-cell responses in the intestine remains unclear. This work will therefore establish the role of NOD2 signaling in initiating and maintaining optimal TRM responses to achieve intestinal homeostasis and resilience to intestinal inflammation.

Purpose

It is the main objective of this project to determine whether NOD2-mediated signalling affects:

1. Antigen-specific T-cell priming in vivo

2. Bona fide intestinal T_RM generation

3. Bona fide intestinal T_RM function

Method

To address the effects of NOD2-signalling on intestinal T-cell priming in vivo, wildtype (WT) mice were adoptively transferred 50,000 naïve LCMV-specific (SMARTA) CD4⁺ T-cells. Mice were subsequently infected with LCMV-Armstrong in the presence or absence of the NOD2 agonist; MDP. 5-days following infection, the numbers and percentage of LCMV-specific T-cells in the mesenteric lymph nodes and spleen were examined. To examine the effects of NOD2 on intestinal T_RM generation, littermate WT and NOD2 KO mice were infected with LCMV-Armstrong. Thirty-six-days following infection, the percentage and number of LCMV-specific CD4⁺ T-cells were profiled in the small and large intestinal lamina-propria by means of gp_66-77 class-II MHC-tetramer staining. In another set of experiments, littermate WT and NOD2 KO mice were re-infected with LCMV-C13 30-days following LCMV-Armstrong immunization, and the interferon-response in the small intestine was profiled by quantitative PCR to assess the effect of NOD2-deficiency on antigen recall responses.

Result(s)

NOD2-stimulation by means of MDP injection increased the percentage and number of adoptively transferred SMARTA CD4⁺ T-cells in the mesenteric lymph nodes upon LCMV infection. Furthermore, NOD2-deficiency did not alter intestinal LCMV-specific CD4⁺ T_RM seeding in the small and large intestinal lamina propria 36 days after infection. However, in vivo antigen recall experiments showed a decreased intestinal IFN response in NOD2 KO mice.

Conclusion(s)

Our findings reveal a potential role of NOD2 in the intestinal CD4⁺ T-cell priming and subsequent Ag-specific memory response.

Disclosure of Interest

None Declared

A235 THE INFLUENCE OF IL10 ON COLITIS DEVELOPMENT IN NOD2 DEFICIENT MICE

Background

Inflammatory bowel disease (IBD) risk genes include interleukin-10 (IL10) and nucleotide-binding oligomerization domain-containing protein 2 (NOD2). Although their specific roles in intestinal inflammation are unclear, these proteins are involved in modulating host-microbe interactions and intestinal homeostasis.

Aims

Since IL10 is an anti-inflammatory cytokine that maintains intestinal homeostasis, we hypothesized that mice deficient for both IL10 and NOD2 would be more susceptible to colitis than mice with only the NOD2 deletion.

Methods

In-house generated NOD2-/- x IL10-/- (double knockout) and NOD2-/- x IL10+/+ littermate mice of varying ages (3–20 weeks of age) were weighed and stools samples were collected at weekly intervals. Lipocalin-2 (LCN-2) levels were quantified in stool by ELISA. A subset of mice from each genotype received 3.5% dextran sulfate sodium (DSS) supplemented water for 5 days starting at eight weeks of age. Mice were sacrificed after two days of regular water, on day 8.

Results

Untreated NOD2-/- x IL10+/+ mice showed higher fecal LCN-2 compared to NOD2-/- x IL10-/- mice at all ages, although this trend was not significant. Within DSS-treated mice, LCN-2 levels in stool collected at sacrifice (on day 8) were significantly higher in NOD2-/- x IL10+/+ mice, compared to NOD2-/- x IL10-/- mice. Moreover, only 50% (2 of 4) of the NOD2-/- x IL10+/+ DSS-treated mice survived to day 8, whereas all four NOD2-/- x IL10-/- DSS-treated mice survived.

Conclusions

Fecal LCN-2 indicates the extent of neutrophil infiltration, which is reflective of the severity of intestinal inflammation. As such, LCN-2 levels suggest that NOD2-/- x IL10+/+ mice have higher baseline inflammation and are more susceptible to DSS-induced colitis than double knockout NOD2-/- x IL10-/- mice. These results are contrary to our hypothesis that combining IL10 and NOD2 deficiency would increase colitis susceptibility as compared to NOD2 deficiency alone. This suggests that the absence of IL10 may actually reduce the severity of DSS-induced colitis in NOD2 deficient mice. The role of IL10 in modulating the gut microbiome using this model remains to be assessed.

Funding Agencies

CAG