Drake, Li Yin

Summary Interleukin ( IL )‐33 is a key cytokine involved in type 2 immunity and allergic airway diseases. Abundantly expressed in lung epithelial cells, IL ‐33 plays critical roles in both innate and adaptive immune responses in mucosal organs. In innate immunity, IL ‐33 and group 2 innate lymphoid cells ( ILC 2s) provide an essential axis for rapid immune responses and tissue homeostasis. In adaptive immunity, IL ‐33 interacts with dendritic cells, Th2 cells, follicular T cells, and regulatory T cells, where IL ‐33 influences the development of chronic airway inflammation and tissue remodeling. The clinical findings that both the IL ‐33 and ILC 2 levels are elevated in patients with allergic airway diseases suggest that IL ‐33 plays an important role in the pathogenesis of these diseases. IL ‐33 and ILC 2 may also serve as biomarkers for disease classification and to monitor the progression of diseases. In this article, we reviewed the current knowledge of the biology of IL ‐33 and discussed the roles of the IL ‐33 in regulating airway immune responses and allergic airway diseases.

Abstract Innate lymphoid cells (ILCs) are a new family of immune cells that play important roles in innate immunity in mucosal tissues, and in the maintenance of tissue and metabolic homeostasis. Recently, group 2 ILCs (ILC2s) were found to promote the development and effector functions of Th2-type CD4+ T cells by interacting directly with T cells or by activating dendritic cells, suggesting a role for ILC2s in regulating adaptive immunity. However, our current knowledge on the role of ILCs in humoral immunity is limited. In this study, we found that ILC2s isolated from the lungs of naive BALB/c mice enhanced the proliferation of B1- as well as B2-type B cells and promoted the production of IgM, IgG1, IgA, and IgE by these cells in vitro. Soluble factors secreted by ILC2s were sufficient to enhance B cell Ig production. By using blocking Abs and ILC2s isolated from IL-5–deficient mice, we found that ILC2-derived IL-5 is critically involved in the enhanced production of IgM. Furthermore, when adoptively transferred to Il7r−/− mice, which lack ILC2s and mature T cells, lung ILC2s promoted the production of IgM Abs to a polysaccharide Ag, 4-hydroxy-3-nitrophenylacetyl Ficoll, within 7 d of airway exposure in vivo. These findings add to the growing body of literature regarding the regulatory functions of ILCs in adaptive immunity, and suggest that lung ILC2s promote B cell production of early Abs to a respiratory Ag even in the absence of T cells.