D1.134 - Type 2 innate lymphoid cells promote development and differentiation of neonatal lung stem/progenitor activity

The immune environment of the neonatal lung is inherently biased toward type 2 immunity. This response is primarily driven by interleukin-33 (IL-33), which is spontaneously released from alveolar type 2 cells in response to birth-associated stress. IL-33 subsequently promotes the activation and expansion of group 2 innate lymphoid cells (ILC2s), leading to a transient surge of type 2 cytokines during early life. This neonatal type 2 response is abolished in IL-33- or ST2-deficient mice. Moreover, neonatal exposure to allergens or supplemental oxygen exacerbates type 2 inflammation, characterized by enhanced ILC2 activation, and results in more severe airway inflammation following allergen challenge in adulthood. Despite these observations, the role of ILC2s in neonatal lung development remains poorly understood. Because postnatal lungs are still actively developing, we hypothesized that ILC2s may contribute to neonatal lung growth. We previously identified an SSEA-1–expressing lung epithelial population in neonatal lungs (neonatal SSEA-1⁺ lung stem/progenitor cells) that exhibits stem/progenitor activity in lung organoid formation.

Neonatal lung–derived stem/progenitor cells were embedded in Matrigel to generate lung organoids. To assess the role of ILC2s in neonatal lung epithelial development, ILC2s were either co-embedded with neonatal lung–derived stem/progenitor cells or cultured outside the Matrigel matrix to distinguish cell contact–dependent and –independent effects.

Neonatal SSEA-1⁺ lung stem/progenitor cells progressively formed lung organoids during in vitro 3D culture. Organoid formation was significantly enhanced when these cells were co-cultured with ILC2s, both in cell contact–dependent and contact-independent settings, with direct cell contact producing the strongest effect. These findings indicate that ILC2s promote neonatal lung stem/progenitor cell activity and organoid development. However, prolonged ILC2 activation led to increased goblet cell differentiation and mucus production in the resulting lung organoids, features commonly associated with allergic airway inflammation, suggesting aberrant epithelial differentiation under sustained ILC2 stimulation.

Our results suggest that transient accumulation and activation of ILC2s in neonatal lungs may support lung stem/progenitor cell activity and postnatal lung growth, whereas prolonged ILC2 stimulation disrupts epithelial homeostasis by promoting goblet cell differentiation. These findings highlight the importance of finely tuned immune regulation in the neonatal lung.