Rolle von NF-kappaB-abhängigen proinflammatorischen Mastzellfunktionen in Immunantworten
Zusammenfassung der Projektergebnisse
Mast cells (MCs) are tissue resident hematopoietic cells found in most tissues. They are widely regarded as important sentinel cells that amplify local innate responses and adjuvant adaptive immunity. This view, however, was primarily based on experiments in Kit-mutant mast cell-deficient mouse strains. Since the reliability of these mouse strains as mast celldeficiency models was recently challenged, a systematic re-evaluation of mast cell functions in the immune system is mandatory. The aim of the present project was to investigate the role of mast cells in immune responses and the contribution of NF-κB signaling in mast cells to immune functions of these cells based on novel, Kit-independent mouse models of mast cell-deficiency and mast cell-specific gene inactivation. Mast cells are the key effector cells in allergic disease, including asthma. In a first part of the project, we sought to clarify the role of mast cell NF-κB signaling in IgE-mediated mast cell responses. A previous study based on Kit-mutant mice published in CELL described an essential role for IKK2 in IgE-mediated mast cell degranulation. We used mice with mast cellspecific knock out of IKK2 or NEMO and mice with mast cell-specific expression of a mutant, constitutively active IKK2 and analyzed mast cell responses to IgE crosslinking in vitro and in vivo. We unexpectedly found that neither loss IKK2 or NEMO nor over-activity of the NFkB pathway had a detectable effect on the early degranulation response. The late phase cytokine response triggered by IgE crosslinking, however, was found to be dependent on NF-κB signaling as expected. The finding that IKK2 had no role in initiation of granule release is important because this means that the search for proteins coupling FceR signaling to the vesicle exocytosis machinery of the mast cell must continue. In a second part of the project, we aimed to clarify in what way mast cells and NFkB signaling in mast cells contribute to IgE-independent innate and adaptive immune responses. Based on numerous experiments Kit-mutant MC-deficient mice, mast cells are generally regarded as important amplifiers of innate immune responses that provide essential adjuvant effects for adaptive immunity. We attempted to reproduce these literature findings in our novel Kit-independent mast cell deficiency model. We immunized mast cell-deficient Mcpt5- Cre R-DTA and control mice with protein antigens plus adjuvant and quantified the antigenspecific T cell and antibody responses. Unexpectedly, we found that the absence of mast cells did not detectably impair the immune responses. Activation of mast cells by mast cell secretagogues including compound 48/80 had been proposed as a novel vaccine adjuvant principle. We confirmed that c48/80 has potent adjuvant activity but showed that this was completely independent of the presence or absence of mast cells. Collectively, our findings unambiguously demonstrated that innate MC responses to adjuvants in the tissues are not required for efficient stimulation of T and B cell responses. Thus, our original question of the role of mast cell NF-κB signaling in adaptive immunity was obsolete. Our results are at sharp conflict with published reports on MC functions in adaptive immunity and add to a long list of cases in which findings in Kit mutant mouse strains did not reproduce in one of the novel mouse strains with Kit-independent selective MC-deficiency but otherwise normal immune system. Our findings indicate that functions of MCs in adaptive immunity beyond pathophysiological functions in IgE-mediated allergic disease may be much more restricted than previously concluded from experiments in Kit-mutant strains.
Projektbezogene Publikationen (Auswahl)
- (2018) Unimpaired Responses to Vaccination With Protein Antigen Plus Adjuvant in Mice With Kit-Independent Mast Cell Deficiency. Frontiers in immunology 9 1870
Schubert, Nadja; Lisenko, Katharina; Auerbach, Christian; Weitzmann, Anke; Ghouse, Shanawaz Mohammed; Muhandes, Lina; Haase, Christa; Häring, Tobias; Schulze, Livia; Voehringer, David; Gunzer, Florian; Müller, Werner; Feyerabend, Thorsten B.; Rodewald, Ha
(Siehe online unter https://doi.org/10.3389/fimmu.2018.01870) - 2014. IκB kinase 2 is essential for IgE-induced mast cell de novo cytokine production but not for degranulation. Cell Reports 8: 1300–1307
Peschke, K., Weitzmann, A., Heger, K., Behrendt, R., Schubert, N., Scholten, J., Voehringer, D., Hartmann, K., Dudeck, A., Schmidt-Supprian, M., Roers, A.
(Siehe online unter https://doi.org/10.1016/j.celrep.2014.07.046) - Mucosal mast cells are indispensable for the timely termination of Strongyloides ratti infection. Mucosal Immunol. 2016
Reitz M, Brunn ML, Rodewald HR, Feyerabend TB, Roers A, Dudeck A, Voehringer D, Jönsson F, Kühl AA, Breloer M
(Siehe online unter https://doi.org/10.1038/mi.2016.56)
