Th2

Overview

T helper 2 (Th2) cells are a subset of CD4+ T cells that play a crucial role in the immune system, particularly in the context of allergic reactions and helminth infections. Th2 cells are characterized by their production of a specific set of cytokines, including interleukin-4 (IL-4), interleukin-5 (IL-5), interleukin-9 (IL-9), interleukin-10 (IL-10), and interleukin-13 (IL-13). These cytokines are involved in the activation and recruitment of eosinophils, basophils, and mast cells, as well as the promotion of IgE production by B cells.

Differentiation

Th2 cell differentiation is initiated when naive CD4+ T cells are exposed to antigen-presenting cells (APCs) that present antigens in the context of MHC class II molecules. The presence of IL-4 is critical for the differentiation of Th2 cells. IL-4 activates the transcription factor GATA3, which in turn promotes the expression of Th2-specific cytokines and inhibits the differentiation of Th1 cells.

Function

Th2 cells are primarily involved in humoral immunity and are essential for the defense against extracellular parasites, such as helminths. They also play a significant role in the pathogenesis of allergic diseases, such as asthma, allergic rhinitis, and atopic dermatitis. The cytokines produced by Th2 cells lead to the activation and recruitment of eosinophils and mast cells, which are key effector cells in allergic inflammation.

Cytokine Profile

• IL-4: Promotes B cell class switching to IgE and IgG1, and is crucial for Th2 differentiation.
• IL-5: Stimulates the growth and activation of eosinophils.
• IL-9: Enhances mast cell growth and function.
• IL-10: Has anti-inflammatory properties and can inhibit Th1 responses.
• IL-13: Similar to IL-4, it promotes IgE production and is involved in airway hyperresponsiveness.

Clinical Significance

Th2 cells are implicated in various allergic conditions. The overproduction of Th2 cytokines can lead to chronic inflammation and tissue damage, as seen in asthma and other allergic diseases. Therapeutic strategies targeting Th2 cytokines, such as monoclonal antibodies against IL-4, IL-5, and IL-13, have been developed to treat these conditions.

Also see

• Th1 cells
• Th17 cells
• Regulatory T cells
• Cytokines
• Immune system