Simone Keck, PhD

• Member of Swiss Society for Allergology and Immunology (SSAI/SGAI)
• Member of UniBasel Immunology Community (UBICO)
• Member of Society for Mucosal Immunology

• Best experimental pediatric research project, UKBB Research Day 2016

1. Role of colonic immune cell phenotypes and extrinsic nerve fiber density in in the manifestation of Hirschsprung's disease associated enterocolitis.
Hirschspung's disease (HD) associated enterocolitis is responsible for half of the deaths associated with Hirschsprung's disease. The fact that it could develop even after removal of affected tissue suggests an extension of neuroregulatory defects into immune cells.
In healthy patients the enteric nervous system controls and synapses with in-coming extrinsic nerve fibers originating from pelvic ganglion. By the lack of ENS, HD patients show a hyper-innervation with cholinergic acetylcholine (Ach) secreting extrinsic nerve fibers in the distal colon region, restricted to rectum and sigmoid colon. Detecting those Ach-positive fibers in a rectum biopsy represents the gold standard for histo-pathological HD diagnosis.
Recently, acetylcholine was described in the literature as an immune modulatory component. It activates either muscarinic (M1-M5) or nicotinic receptors (composition of heteromeric and homomeric subtypes including α2-α10 and β2-β4) expressed by target cells. The α7 nicotinic Ach receptor (α7nAchR) is expressed by various immune cells including macrophages. Tracey et. al described the first time the control of an immune response by activation of α7nAchRs expressed on macrophages and named it subsequently the anti-inflammatory cholinergic reflex (Borovikova et al., nature, 2000). Activation of α7nAchR during bacterial invasion/recognition downregulates inflammatory cytokines to prevent excessive immune activation and tissue pathology. However, under homeostatic conditions, strong cholinergic signals may favor a macrophage phenotype unable to control and kill invading bacteria leading to bacterial accumulation and manifestation of enterocolitis.
We aim to characterize the immune cell phenotypes of variuos innate and adaptive immune cells and how this correlates to the degree of cholinergic fiber innervation and bacterial load in fresh colonic tissue of HD patients (NIG-Study, Basel: Swiss-and German wide multicentric study). Using combined tissue analysis (RNA analysis, histology, 16s fluorescent in situ hybridization (FISH), immune cell phenotyping by flow-cytometric analysis) and clinical follow up of enterocolitis manifestation we anticipate to find new immune cell specific neuronal signalling pathways. Using this personalized tissue analysis we expect to define patients at high risk to develop an enterocolitis. We anticipate to find new potential compounds for therapeutic interventions of HD associated enterocolitis.

2. Contribution of neuroregulators in the control of different immune cell types and the development of HD associated enterocolitis
HD represents a multi-genetic congenital malformation of the intestine involving gen defects responsible for neural crest cell migration during embryogenesis. The two main signaling pathways involved in neural crest migrations are the RET receptor and endothelin-receptor beta (EDNRB) signalling pathways often impaired in HD patients resulting in the lack of enteric ganglia in the distal colon. Recently, it has been shown that the neuroregulator EDNRB plays an important role in the formation of functional B-cell follicles (3). Additionally, it is reported that innate lymphoid cell type 3 (ILC3) specific deletion of Ret leads to an increased suceptibility to intestinal infections (4).
We aim to screen intestinal tissue of HD patients for the underlying genetic defect and the involved defect neuroregulator. Individual immune cells (macrophages, ILC3, T cells) from fresh colonic tissue of HD patients will be sorted by fluoresence-activated cell sorting (FACS). This enables us to do next-generation RNA sequencing to uncover a possible involvement of immune cell specific neuroregulators in colitis manifestation.
Clinical Collaborators Neuro-Immune Study Basel (NIG-Study):
Participating padiatric surgery units: Zürich, Bern, Genf, Lausanne, St. Gallen, Luzern, Bellinzona, Heidelberg (DE), Karlsruhe (DE) and Düsseldorf (DE)