Dissecting ILC2 - eosinophil crosstalk in development and inflammation

• Applicant: Professor Dr. Christoph Siegfried Niki Klose
• Subject Area: Immunology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 550050344

Type 2 immune responses protect against worm infections but can become detrimental when triggered against non-infectious environmental stimuli. Eosinophils are a hallmark of type 2 responses and contribute to tissue damage and inflammation occurring when type 2 responses are initiated. We could recently show that eosinophils are strictly dependent on signals that group 2 innate lymphoid cells (ILC2) provide. Eosinophils do not develop in normal proportions in ILC2-deficient Nmur1eGFP-2A-Cre Id2flox/flox mice and are not effectively recruited in tissues during allergic lung inflammation. However, the factors released by ILC2, as well as their regulation, require more investigation. Nmur1eGFP-2A-Cre mice for gene targeting in ILC2 allow us to examine upstream and downstream mediators of ILC2 - eosinophil interaction. Based on our preliminary data, we have already started to generate ILC2-specific conditional knockout mice for IL-5 and GM-CSF as effector cytokines required for eosinophils (Nmur1eGFP-2A-Cre Il5flox/flox and Nmur1eGFP-2A-Cre Csf2flox/flox). In Aim 1, we will study the effects of ILC2 deficiency on eosinophil development and expansion using the aforementioned conditional knockout mice. To this end, we will employ an established high-resolution flow cytometry panel to dissect eosinophil development in the absence of ILC2. Further, we will perform InfinityFlow as an open-ended approach to dissect eosinophil development at high resolution. Since eosinophils are ILC2-dependent, we hypothesize that ILC2 and eosinophils occupy niches in the bone marrow, where they can functionally interact, supporting their development. We will use microscopy of reporter mice together with imaging to discover whether ILC2 and eosinophils form functional clusters in the bone marrow. In Aim2, we will thoroughly investigate how IL-5 regulates eosinophil response in different models of allergic lung inflammation provoked by house dust mite or Alternaria alternata extract exposure. For this purpose, we will use fluorescent eosinophils from IL5RAporter mice in combination with Il5-/- mice. This will allow us to track the movement and behavior of eosinophils in response to IL-5. In Aim 3, we will clarify the impact of the anti-IL-4R antibody dupilumab on lung eosinophilia and assess how it correlates with the quality of the clinical response to treatment. To better understand how IL-4R regulates type 2 immune responses, we will use conditional knockout mice of Il4ra in ILC2 and eosinophils to delineate the importance of the signaling pathway for each type as well as the crosstalk between these two innate immune cell populations. Delineating the crosstalk between ILC2 and eosinophils will be crucial to understand how type 2 immune responses are orchestrated. Using both focused and global experimental approaches, our research has the potential to discover novel molecular pathways which can be harnessed for the prevention and therapy of type 2 diseases.

• DFG Programme: Research Grants
• International Connection: Belgium
• Partner Organisation: Fonds National de la Recherche Scientifique - FNRS
• Cooperation Partner: Dr. Christophe J. Desmet