C17 Prevents Inflammatory Arthritis and Associated Joint Destruction in Mice

C17 was first described about ten years ago as a gene expressed in CD34+ cells. A more recent study has suggested a role for C17 in chondrogenesis and development of cartilage. However, based on sequence analysis, we believe that C17 has homology to IL-2 and hence we present the hypothesis that C17 is a cytokine possessing immune-regulatory properties. We provide evidence that C17 is a secreted protein preferentially expressed in chondrocytes, hence in cartilage-rich tissues. Systemic expression of C17 in vivo reduces disease in a collagen antibody-induced arthritis model in mice (CAIA). Joint protection is evident by delayed disease onset, minimal edema, bone protection and absence of diverse histological features of disease. Expression of genes typically associated with acute joint inflammation and erosion of cartilage or bone is blunted in the presence of C17. Consistent with the observed reduction in bone erosion, we demonstrate reduced levels of RANKL in the paws and sera of mice over-expressing C17. Administration of C17 at the peak of disease, however, had no effect on disease progression, indicating that C17's immune-regulatory activity must be most prominent prior to or at the onset of severe joint inflammation. Based on this data we propose C17 as a cytokine that s contributes to immune homeostasis systemically or in a tissue-specific manner in the joint

Circulating and gut-resident human Th17 cells express CD161 and promote intestinal inflammation

The C-type lectin-like receptor CD161, which has recently been described to promote T cell expansion, is expressed on a discrete subset of human CD4 T cells. The function of such cells, however, has remained elusive. We now demonstrate that CD161+ CD4 T cells comprise a circulating and gut-resident T helper 17 (Th17) cell population. During Crohn's disease (CD), these CD161+ cells display an activated Th17 phenotype, as indicated by increased expression of interleukin (IL)-17, IL-22, and IL-23 receptor. CD161+ CD4 T cells from CD patients readily produce IL-17 and interferon γ upon stimulation with IL-23, whereas, in healthy subjects, priming by additional inflammatory stimuli such as IL-1β was required to enable IL-23–induced cytokine release. Circulating CD161+ Th17 cells are imprinted for gut homing, as indicated by high levels of CC chemokine receptor 6 and integrin β7 expression. Supporting their colitogenic phenotype, CD161+ Th17 cells were found in increased numbers in the inflammatory infiltrate of CD lesions and induced expression of inflammatory mediators by intestinal cells. Our data identify CD161+ CD4 T cells as a resting Th17 pool that can be activated by IL-23 and mediate destructive tissue inflammation

Antitumor efficacy of combined CTLA4/PD-1 blockade without intestinal inflammation is achieved by elimination of FcγR interactions

Background Programmed cell death protein 1 (PD-1) and CTLA4 combination blockade enhances clinical efficacy in melanoma compared with targeting either checkpoint alone; however, clinical response improvement is coupled with increased risk of developing immune-related adverse events (irAE). Delineating the mechanisms of checkpoint blockade-mediated irAE has been hampered by the lack of animal models that replicate these clinical events.Methods We have developed a mouse model of checkpoint blockade-mediated enterocolitis via prolonged administration of an Fc-competent anti-CTLA4 antibody.Results Sustained treatment with Fc-effector, but not Fc-mutant or Fc-null, anti-CTLA4 antagonist for 7 weeks resulted in enterocolitis. Moreover, combining Fc-null or Fc-mutant CTLA4 antagonists with PD-1 blockade results in potent antitumor combination efficacy indicating that Fc-effector function is not required for combination benefit.Conclusion These data suggest that using CTLA4 antagonists with no Fc-effector function can mitigate gut inflammation associated with anti-CTLA4 antibody therapy yet retain potent antitumor activity in combination with PD-1 blockade

LAG3 Regulatory T Cells Restrain Interleukin-23-Producing CX3CR1 Gut-Resident Macrophages during Group 3 Innate Lymphoid Cell-Driven Colitis.

Interleukin-22 (IL-22)-producing group 3 innate lymphoid cells (ILC3) maintains gut homeostasis but can also promote inflammatory bowel disease (IBD). The regulation of ILC3-dependent colitis remains to be elucidated. Here we show that Foxp3 regulatory T cells (Treg cells) prevented ILC3-mediated colitis in an IL-10-independent manner. Treg cells inhibited IL-23 and IL-1β production from intestinal-resident CX3CR1 macrophages but not CD103 dendritic cells. Moreover, Treg cells restrained ILC3 production of IL-22 through suppression of CX3CR1 macrophage production of IL-23 and IL-1β. This suppression was contact dependent and was mediated by latent activation gene-3 (LAG-3)-an immune checkpoint receptor-expressed on Treg cells. Engagement of LAG-3 on MHC class II drove profound immunosuppression of CX3CR1 tissue-resident macrophages. Our study reveals that the health of the intestinal mucosa is maintained by an axis driven by Treg cells communication with resident macrophages that withhold inflammatory stimuli required for ILC3 function

C17 protein is monomeric.

<p>(A) Recombinant purified human C17-V5H8 was analyzed by SDS-PAGE under reducing (1) and non-reducing (2) loading conditions and subsequent Coomassi staining. A protein marker is shown in the right column (3). (B) Baseline drift-corrected A280 nm elution profile of size exclusion chromatography after loading affinity-purified human C17-V5H8. Retention times of marker proteins (in kDa) are indicated above.</p

Reduced expression of inflammatory markers and genes associated with joint destruction in paws of C17-treated animals.

<p>One hind paw per animal was harvested at the time of euthanasia and quantitative RT-PCR was performed to measure mRNA levels of cytokines associated with joint inflammation (A), and genes associated with joint remodeling and arthritic tissue destruction (B). (C) mRNA expression of selected genes from paws with severe swelling and matched clinical disease score 3. (D) C17 expression in paws from naïve animals and animals that received arthrogen with GFP control or C17 minicircle. Values from naïve animals are shown as filled triangles, from GFP mice as filled squares, from C17 mice as open circles, throughout the figure. Not significant: ns; p<0.05: *; p<0.01: **. Similar data were obtained in at least two independent experiments with five or more mice per group.</p

C17 mRNA and protein are expressed in cartilage-rich tissues and chondrocytes, respectively.

<p>(A) A variety of tissues were harvested and pooled from three C57BL/6 mice and then analyzed for C17 mRNA expression using qPCR (n.d., not detected). (B) Immunohistochemical staining for C17 on mouse sternal cartilage, using a mAb anti-C17, demonstrates protein expression by chondrocytes. Scale bars represent 0.1 mm.</p

Bone erosion and histological parameters of arthritis are reduced in mice over-expressing C17.

<p>One hind paw per animal was harvested at the time of euthanasia and was analyzed by micro-CT and subsequent histology. (A) Representative histology images from individual hind paws are shown either stained with H&E (top row) or stained with Safranin O (bottom row). Images were taken at 10× magnification. (B) Scoring of disease severity according to diverse histological parameters. (C) Representive micro-CT scans are shown. Red box highlights prominent joint erosion in paw of GFP treated mouse. Similar data were generated in at least three independent experiments with at least five animals per group.</p