Type 2 immunity in the skin and lungs

Area of Science:

• Immunology
• Allergic Diseases
• Dermatology
• Pulmonology

Background:

• Asthma and atopic dermatitis (AD) are characterized by type 2 immune responses.
• Epithelial-derived cytokines like IL-25, IL-33, and thymic stromal lymphopoietin are central to initiating type 2 responses.
• Th2 cells and innate lymphoid cells (ILC) are key producers of type 2 cytokines (IL-4, IL-5, IL-9, IL-13).

Purpose of the Study:

• To review recent advancements in understanding type 2 immunity in allergic skin and lung diseases.
• To discuss the cellular sources, targets, and functions of type 2 immune mechanisms in asthma and AD.
• To highlight the complexity of type 2 immunity and its implications for treatment.

Main Methods:

• Review of current literature on cellular and molecular mechanisms of type 2 inflammation.
• Analysis of the roles of specific cytokines (IL-4, IL-5, IL-13, IL-9) and immune cells (Th2, ILC) in allergic diseases.
• Examination of the efficacy and limitations of current biologic therapies targeting type 2 pathways.
• Inclusion of insights from primary immune deficiency diseases to understand type 2 immune component redundancy.

Main Results:

• IL-4 and IL-13 promote IgE class-switching in B cells and contribute to T-cell and eosinophil migration.
• IL-13 influences epithelial cell function, mucus production, smooth muscle contraction, and barrier integrity.
• IL-5 is critical for eosinophil activation, recruitment, and survival; IL-9 enhances the allergic phenotype.
• Type 2 ILC amplify inflammation in AD and asthma by boosting Th2 cell and eosinophil activity.
• Current biologics target IgE, IL-5, or IL-4 receptor alpha, but some patients with severe disease do not respond.

Conclusions:

• Type 2 immune responses are complex and involve multiple interacting cellular and molecular components.
• Despite advances and targeted therapies, significant unmet needs exist for patients unresponsive to current biologics.
• Further research into the intricacies of type 2 immunity, including insights from immune deficiencies, is essential for improved therapeutic strategies.