IL-4

Interleukin-4 (IL-4) is a critical Th2 cytokine that regulates immune responses by promoting differentiation of naive CD4⁺ T cells into Th2 cells^[1]. Mechanistically, IL-4 activates the JAK-STAT6 signaling pathway, leading to transcriptional induction of genes involved in humoral immunity, including IgE class switching in B cells^[1]. In disease models, IL-4 contributes to the pathogenesis of allergic inflammation and asthma by inducing eosinophilia, mucus hyperproduction, and alternatively activated macrophages^[1]. Compared with related isoforms such as IL-13, IL-4 exhibits unique receptor engagement, preferentially signaling through IL-4Rα paired with the common gamma chain, which defines distinct cellular responses^[1]. IL-4 agonists and inhibitors have been applied in experimental research to modulate Th2-skewed immune responses, enabling the study of allergic airway inflammation and potential therapeutic interventions^[1]. Experimental blockade of IL-4 reduces IgE production and airway hyperreactivity, confirming its central role in type 2 immunity and providing a framework for targeted immunomodulation in preclinical models^[1]. Therefore, IL-4 serves as both a mechanistic marker and a modifiable factor in studies of cytokine-driven inflammation.