Functional analysis of the interleukin-27-induced antigen processing and presentation on oral and intestinal mucosal surfaces

• Applicant: Dr. Julia Diegelmann
• Subject Area: Gastroenterology ; Biochemistry ; Dentistry, Oral Surgery
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274182912

In the human immune system, (foreign) antigens are bound by MHC class I and class II receptors and are presented to immune cells. While MHCI receptors are expressed on nearly all somatic cells, MHCII receptors are mainly found on the surface of professional antigen-presenting cells (APCs). Besides specialized cells of the immune system, cells of mucosal surfaces such as intestinal epithelial cells (IEC) of the digestive tract as well as oral epithelial cells (OEC) of the oral cavity play an important role in immune defence. They are constantly in contact with commensal and pathogenic bacteria and produce thereupon pro- and anti-inflammatory cytokines in a balanced manner. If this fine-tuned reaction is disturbed, this may lead to excessive immune responses and subsequently to chronic inflammation such as inflammatory bowel disease (IBD) and chronic periodontitis (CP). Interleukin-27 (IL-27) is a cytokine that plays an important role in the differentiation of several T cell types and its expression is increased in IBD patients. Own analyses have shown that IL-27 also is protective for the intestinal barrier and induces expression of anti-inflammatory and anti-bacterial proteins in IEC. Preliminary microarray analyses indicated that IL-27 up-regulates CIITA, the master transcription factor necessary for MHC class II expression, as well as other genes of the MHC locus in IEC and OEC thereby potentially enabling these cells to act as non-professional APCs. Based on these preliminary studies, the goal of this proposal is a detailed functional analysis of the IL-27-induced antigen presentation in IEC and OEC. Further genes directly or indirectly involved in antigen processing and presentation (e.g. immunoproteasome) are to be identified and the involved signal transduction pathways and regulatory DNA elements will be analyzed in detail. For this purpose, molecular biology techniques such as western blot, siRNA transfection, EMSA, ChIP, Co-IP, immunofluorescence and luciferase assays will be applied. To analyze the role of IL-27 in inducing MHC molecules and intestinal antigen presentation, epithelial-specific IL-27 receptor knockout mice will be generated (using the Cre-lox system with Cre recombinase expressed under control of the epithelial-specific villin promoter) and will be analyzed in the T cell adoptive transfer model of colitis. Moreover, tissue biopsies from healthy subjects and IBD and CP patients will be analyzed by immunohistochemistry for expression of MHC molecules. Double stainings with antibodies against cell type specific markers will be used to determine the cellular subtype in which MHC expression is present. The results of this proposal will contribute to our knowlegde of IBD and CP pathogenesis and will help to better understand the role of cells on mucosal surfaces as non-professional APCs.

• DFG Programme: Research Grants