T-helper 2 and T-helper 17 immune response pathways (Th2/Th17 pathways)

The T-helper 2 (Th2) and T-helper 17 (Th17) immune response pathways are two distinct arms of the adaptive immune system that coordinate host defense and inflammatory responses. The Th2 pathway, characterized by the production of cytokines such as IL-4, IL-5, and IL-13, is primarily involved in the defense against helminthic parasites and the mediation of allergic inflammation, playing a central role in diseases like atopic dermatitis and asthma [1.1.1, 1.2.1]. The Th17 pathway produces cytokines including IL-17A, IL-17F, and IL-22, which are essential for protecting mucosal surfaces against extracellular pathogens but are also key drivers of autoimmune conditions such as psoriasis and rheumatoid arthritis when dysregulated [1.2.4, 1.3.2]. These pathways are highly targeted in modern medicine through biologics that neutralize specific cytokines or their receptors, as well as small-molecule inhibitors of the Janus kinase (JAK) family that block downstream signaling [1.2.1, 1.2.4]. A significant clinical challenge in targeting these pathways is immune drift, where the therapeutic suppression of one axis can lead to a compensatory overactivation of the other, resulting in new inflammatory symptoms [1.1.4]. Monitoring biomarkers like IgE, eosinophil counts, and specific cytokine levels is crucial for tailoring these therapies to individual patient endotypes [1.4.1].

Other names

Th2/Th17 axisType 2 and Type 17 immune pathwaysT-helper 2 and T-helper 17 signalingTh2/Th17 cytokine network

Drugs targeting these pathways function by neutralizing key effector cytokines (e.g., IL-4, IL-13, IL-17A) or their receptors (e.g., IL-4Rα, IL-17RA) to suppress downstream inflammatory signaling, or by using Janus kinase (JAK) inhibitors to block the intracellular signal transduction of multiple cytokines involved in T-cell differentiation and activation.