Tissue specific regulation of human ILC2 in allergy and asthma

<p dir="ltr">Asthma is one of the most common non-communicable diseases, affecting over 300 million people worldwide. It is a heterogeneous condition comprising several endotypes, yet all share the hallmark of dysregulated immune responses driving airway inflammation. The most prevalent form, type 2-high asthma, is mediated by aberrant activation of type 2 immune cells, including type 2 innate lymphoid cells (ILC2), type 2 T helper (Th2), and type 2 cytotoxic T (Tc2) cells. We and others have previously shown that the phenotype and function of ILC2 are strongly shaped by their microenvironment, but how human ILC2 are regulated in asthma and allergy remains incompletely understood.</p><p dir="ltr">In this thesis, we investigated how metabolic status, biologics therapy, lipid mediators, and epithelial-immune crosstalk shape ILC2 function in asthma. By combining patient cohorts with mechanistic studies, we aimed to clarify the factors that sustain or modulate type 2 airway inflammation. Although this work primarily focused on ILC2, related lymphocytes were also analyzed to capture the broader network of immune cells orchestrating airway inflammation.</p><p dir="ltr">In <b>Paper I</b>, we studied how metabolic dysregulation affects ILC2 function in a cohort of asthmatic individuals with overweight or obesity, well-known risk factors for asthma. In those patients, ILC2 displayed an inflammatory phenotype characterized by elevated CD45RO expression, while IL-7Ra expression correlated with body-fat percentage, suggesting a link between metabolic status and ILC2 activation. Functionally, these ILC2 displayed features of corticosteroid resistance, the mainstay of asthma therapy, suggesting a mechanism underlying poor treatment response.</p><p dir="ltr">In <b>Paper II</b>, we analyzed blood samples from patients with severe asthma before and after initiation of biologics therapy targeting IL-5 (mepolizumab) or IL-4Ra (dupilumab). Type 2 lymphocytes, including ILC2, Th2, and Tc2 cells, accumulated in the circulation during mepolizumab therapy, while ILC2 exhibited a similar trend in patients on dupilumab. ILC2 acquired a mature CD117low phenotype, while Th2 and Tc2 cells adopted a central memory profile in patients on mepolizumab. Single-cell RNA sequencing and stimulation assays of mepolizumab-treated patients further revealed altered expression of tissue-homing receptors and increased inflammatory potential, indicating that biologics may redistribute rather than eliminate pathogenic cells capable of reigniting inflammation once treatment ends.</p><p dir="ltr">In <b>Paper III</b>, we examined how bioactive lipid mediators regulate ILCs. We found that ILC3 produce prostaglandin E2 (PGE2), which enhances their cytokine production, but inhibits ILC2, which instead produce and depend on prostaglandin D2 (PGD2). During ILC2-to-ILC3 transdifferentiation, PGD2 synthesis decreased while PGE2 increased alongside type 3 cytokine production. Despite this metabolic shift, transdifferentiated cells remained sensitive to PGE2 inhibition, indicating incomplete reprogramming and a hybrid ILC2/ILC3 phenotype. Such mixed effector profiles have been observed in chronic inflammatory diseases, including mixed granulocytic asthma, highlighting the need to better understand the regulators of this plasticity.</p><p dir="ltr">In <b>Paper IV,</b> we developed a co-culture model combining both human bronchial epithelial cells (BECs) and ILC2 to study their reciprocal interactions. Rhinovirus (RV) infection of BECs induced TSLP release, which activated ILC2 to produce type 2 cytokines. Notably, BECs from asthmatic donors secreted TSLP even at baseline, sustaining chronic ILC2 activation. These findings highlight epithelial-immune crosstalk as a key driver of persistent airway inflammation in asthma and provide a model for future mechanistic studies.</p><p dir="ltr">Collectively, our findings demonstrate that ILC2 function is dynamically regulated by metabolic, pharmacologic, and tissue-derived signals. The persistence and adaptability of ILC2 and related lymphocytes across different disease contexts may explain why certain asthma phenotypes are difficult to treat and point to new avenues for more precise and effective therapeutic intervention.</p><h3>List of scientific papers</h3><p dir="ltr">I. Sophia Björkander, Paul Maier, Maura Kere, Simon Kebede Merid, <b>Lorenz Wirth</b>, Whitney Weigel, Sandra Ekström, Inger Kull, Anna Bergström, Erik Melén, Jenny Mjösberg, Christopher Andrew Tibbitt. Innate lymphoid cells type 2 and CD8+ T cells are perturbed in overweight and obese individuals with asthma. Allergy 2023 Sep; 78(9):2533-2536. <a href="https://doi.org/10.1111/all.15728" target="_blank">https://doi.org/10.1111/all.15728</a></p><p dir="ltr">II. <b>Lorenz Wirth</b>, Whitney Weigel, Christoper T Stamper, Johan Kolmert, Sabrina de Souza Ferreira, Quirin Hammer, Maria Sparreman Mikus, Jakob Theorell, Lars | Andersson, Ann-Sofie Lantz, Eva Wallen- Nielsen, Anne Petrén, Craig E Wheelock, Apostolos Bossios, Nikolaos Lazarinis, Andrei Malinovschi, Christer Janson, Barbro Dahlén, Thomas Hochdörfer, Christopher Andrew Tibbitt, Sven-Erik Dahlén, Valentyna Yasinska, Jenny Mjösberg. High-Dimensional Analysis of Type 2 Lymphocyte Dynamics During Mepolizumab or Dupilumab Treatment in Severe Asthma. Allergy 2025 Sep; 80(9):2541-2556 <a href="https://doi.org/10.1111/all.16633" target="_blank">https://doi.org/10.1111/all.16633</a></p><p dir="ltr">III. <b>Lorenz Wirth</b>, Whitney Weigel, Efthymia Kokkinou, Johan Kolmert, Anna-Karin Johnsson, Alessandro Quaranta, Craig E Wheelock, Mattias Jangard, Sven-Erik Dahlen, Christopher Andrew Tibbitt, Thomas Hochdorfer, Jenny Mjösberg. PGE2 Enhances Human ILC3 Function But Inhibits ILC2-to-ILC3 Transdifferentiation. [Manuscript]</p><p dir="ltr">IV. Jelena Pesic, <b>Lorenz Wirth</b>, Annemarie Hasselberg, Thomas Hochdörfer, Oliwia Slettengren, Katerina Pardali, Stephen Delaney, Jenny Mjösberg, Henric Olsson and Lena Uller. Exploring Bronchial Epithelial and ILC2 Interactions: A Novel Co-Culture Model for Asthma and Viral Infections. [Manuscript]</p>