Gitta Stockinger: Projects

Plasticity of immune effector cells (Crick-funded)

We are using cytokine 'fate' reporter models to facilitate visualisation and isolation of cells that have committed to particular cytokine expression to study their plasticity in different inflammatory models in vivo. The IL-17 fate reporter mouse established the extensive plasticity of Th17 cells in autoimmunity with a tendency to deviate towards a Th1 like profile and the acquisition of additional cytokines involved in pathology driven by IL-23 (Hirota et al. 2011). However, in the mucosal environment of Peyer's patches Th17 cells adopt the profile of follicular helper T cells and support the induction of IgA producing germinal center B cells (Hirota et al 2013). Ongoing studies are focused on determining the mechanisms underlying Th17 to Tfh plasticity as well as the mechanism underlying their help for IgA responses.

Other cytokine fate reporters we analysed were for IL-9, identifying a crucial role for this cytokine in ILC2 and for IL-22, indicating that ILC3 are major producers under homeostatic conditions, but Th17 cells take over during intestinal infection.

Intestinal Th17 cells appear to be non-inflammatory, in contrast to Th17 cells involved in autoimmune diseases. Thus, therapeutic interventions targeting inflammatory Th17 cells need to safeguard the intestinal beneficial Th17 population. We are studying underlying reasons and mechanisms of this functional diversity.

Fig 1

 

Figure 1: Plasticity of Th17 cells.

Th17 cell plasticity can be beneficial or detrimental depending on tissue site and context. In the small intestine, Th17 cells may convert into IL-10 producing 'ex Th17' Tr1 cells under the influence of TGF-β1 via Smad3 and AhR. In Peyer's patches Th17 cells acquire a follicular helper T cell phenotype and provide help for induction of IgA. During Helicobacter hepaticus infection or infection with Citrobacter rodentium newly induced colonic Th17 cells develop plasticity towards IFN-γ producing 'exTh17' Th1 cells. A similar IL-23-dependent Th17 plasticity is observed in the central nervous system (CNS) during experimental autoimmune encephalomyelitis (EAE). Here 'exTh17' Th1 cells produce a broader spectrum of cytokines, including TNF-α, GM-CSF and IFN-γ. 

Hirota, K; Turner, J-E; Villa, M; Duarte, JH; Demengeot, J; Steinmetz,OM and Stockinger, B (2013)        Plasticity of TH17 cells in Peyer's patches is responsible for the induction of T cell-dependent IgA responses.        Nature Immunology        14, 372-379

Hirota, K; Duarte, JH; Veldhoen, M; Hornsby, E; Li, Y; Cua, DJ; Ahlfors, H; Wilhelm, C; Tolaini, M; Menzel, U; Garefalaki, A; Potocnik, AJ and Stockinger, B (2011) Fate mapping of IL-17-producing T cells in inflammatory responses.  Nature Immunology 12, 255-264

Wilhelm, C; Hirota, K; Stieglitz, B; Van Snick, J; Tolaini, M; Lahl, K; Sparwasser, T; Helmby, H and Stockinger, B (2011) An IL-9 fate reporter demonstrates the induction of an innate IL-9 response in lung inflammation. Nature Immunology 12, 1071-1077 

Ahlfors, H; Morrison, PJ; Duarte, JH; Li, Y; Biro, J; Tolaini, M; Di Meglio, P; Potocnik, AJ and Stockinger, B (2014) IL-22 fate reporter reveals origin and control of IL-22 production in homeostasis and infection. Journal of Immunology 193, 4602-4613

Physiological functions of the aryl hydrocarbon receptor in innate and adaptive immune responses (Wellcome-funded)

In this project we are extending our investigations on the physiological functions of AhR in the immune system by identifying AhR targets on DNA and protein level in different cell types and immunological conditions to gain mechanistic insight into how AhR works. Furthermore, we are focusing on the physiological regulation of AhR signaling via metabolic enzymes such as Cyp1a1 that are induced by AhR activation and subsequently metabolise the agonist in a negative feedback loop. Our recent data have shown that constitutively active Cyp1a1 enzyme, even if restricted to intestinal epithelial cells, results in loss of AhR ligands due to excessive metabolism and a phenotype mimicking that of AhR KO mice (Schiering et al Nature 542, 242 (2017).

Fig 2

Figure 2: Depletion of natural AhR ligands leads to impaired immunity to C. rodentium.

Top row: Colon sections of wildtype mice or mice with hyperactive Cyp1a1 in intestinal epithelial cells stained for E-Cadherin (green), C. rodentium (red) and DAPI (blue) of C. rodentium infected mice. Scale bars represent 100mm.  Bottom row: representative photomicrographs of (H&E) stained colon sections of C. rodentium infected mice (left wildtype, right mice with hyperactive Cyp1a1 in IEC).

Schiering, C; Wincent, E; Metidji, A; Iseppon, A; Li, Y; Potocnik, AJ; Omenetti, S; Henderson, CJ; Wolf, CR; Nebert, DW and Stockinger, B (2017)  Feedback control of AHR signalling regulates intestinal immunity.  Nature 542, 242-245  PubMed abstract

Functional roles of the AhR in the intestine: from homeostasis to cancerogenesis (CRUK-funded)

In recent years studies of AhR deficient mice have revealed a range of physiological AhR functions, mainly in barrier organs such as the skin, lung and intestine. The role of the AhR in the intestine is complex, affecting haematopoietic cells as well as epithelium and involving interactions with the microbiota as well as dietary components both of which are sources for AhR ligands, which are essential to maintain intestinal homeostasis. AhR deficient mice lack important immune cells that support barrier protection in the intestine and are vulnerable to intestinal infections as well as prone to develop caecal and colonic tumours. It appears that chronic underlying inflammation in AhR deficient mice facilitates tumour development, particularly under conventional housing conditions, but baseline susceptibility is present even under SPF conditions.

Our aim is to dissect the pathways of AhR interactions in the intestine using the Cre lox system to restrict AhR deficiency to particular cell types that express AhR. We will particularly focus on mice in which AhR is deleted selectively in intestinal cells in steady state as well as during infection with Citrobacter rodentium, an infection that targets the colon and is known to promote tumour formation in genetically susceptible mice. We are culturing organoids to study epithelial cell development  in the absence or presence of AhR and modulate the AhR pathway with ligands such as dietary components (eg. I3C) or tryptophan metabolites and with antagonists such as CH223181 aim to identify the molecular pathways that are influenced by AhR in epithelial cells and could be linked to promotion or prevention of tumorigenesis. 

Fig 3

Figure 3: AhR ligands

AhR ligands are essential for intestinal homeostasis supporting the survival of ILC3 which are important for production of IL-22 and the formation of tertiary lymphoid tissues. AhR deficiency causes dysbiosis with increased bacterial loads and AhR stimulation promotes regeneration of colonic crypt stem cells.

Gitta Stockinger

Gitta Stockinger

brigitta.stockinger@crick.ac.uk
+44 (0)20 379 61600