Visualization of IL-22 expressing cells during anti-infectious immune responses
Zusammenfassung der Projektergebnisse
Interleukin 22 (IL-22) is a cytokine of the IL-10 family functionally involved in tissue repair and host defense against infections by inducing the production of defensins and regenerating gene family proteins in epithelial cells. Initially, IL-22 was found to be produced by differentiated Th17 lymphocytes, natural killer (NK) cells and a subset of NK-like cells co-expressing markers of the lymphoid tissue inducer (LTi) now termed innate lymphoid cells (ILCs). The actual cellular source of IL-22 production and the biological function of IL-22 producing cell in the course of an infection in different host organs is still ill defined in vivo. The aim of the study proposed was to generate an IL-22 reporter mouse line by inserting an IRES driven YFP fluorescence cassette behind the stop codon of the endogenous IL-22 gene locus by homologous recombination in mouse embryonic stem cells. Repeated attempts to generate correctly targeted ES cell clones were not productive. Thus, an alternative strategy was designed and an IL-22-DTR:YFP BAC transgenic reporter mouse line was generated. A diphtheria toxin receptor:YFP fusion construct was cloned behind the start codon of the Il22 gene into a mouse genomic BAC containing the major parts of the neighboring genes 5’ and 3’ of Il22a. This strategy leads to expression of a DTR-YFP fusion protein under the control of the IL-22 promoter. These transgenic mice allow the visualization of IL-22 expressing cells. In addition, by injection of diphtheria toxin, cells producing IL-22 can be depleted. Therefore the alternative approach bears the advantage of the direct analysis of the biological function of IL-22 producing cells additional to its reporter activity. Expression of IL-22 and YFP could be detected in splenic and small intestinal LP ILCs pointing to a faithful reporter activity. The fact that, IL-22 and YFP were not coexpressed in most cells can most likely be attributed to a probable stochastic monoallelic expression of IL-22 already described for the closely related cytokine IL-10. IL-22 production is dependent on IL-23 in vivo. Therefore, crossing the IL-22-DTR:YFP BACtg reporter to the already existing IL-12/23p40-GFP reporter mouse line will allow for the simultaneous monitoring of the regulating IL-23 producing cells vs. the effector IL-22 producing ones. Additionally, work on the biology of IL-23 in CNS autoimmunity was performed in the context of this project. We could show that CCR4 dependent expression of IL-23 expression by DCs plays a decisive role in experimental autoimmune encephalomyelits, an animal model for multiple sclerosis. In summary, we have generated a combined IL-22 reporter/deletion mouse model that can contribute significantly to the definition of the IL-22 producing cell populations, their interaction partners, and their effector functions during anti-infectious immune responses.
Projektbezogene Publikationen (Auswahl)
- (2012) CC chemokine receptor 4 is required for experimental autoimmune encephalomyelitis by regulating GM-CSF and IL-23 production in dendritic cells. Proc Natl Acad Sci USA 109: 3897-902
Poppensieker K, Otte DM, Schürmann B, Limmer A, Dresing P, Drews E, Schumak B, Klotz L, Raasch J, Mildner A, Waisman A, Scheu S, Knolle P, Förster I, Prinz M, Maier W, Zimmer A, and Alferink J
(Siehe online unter https://doi.org/10.1073/pnas.1114153109)
