Th2

Definition

Th2, or T helper 2 cells, are a subset of CD4+ T cells that play a critical role in the adaptive immune response, particularly in orchestrating responses against extracellular pathogens and allergens. They primarily promote the activation of B cells and the production of antibodies, specifically immunoglobulin E (IgE), which is essential for defense against parasites and plays a significant role in allergic reactions.

5 Must Know Facts For Your Next Test

1. Th2 cells are characterized by their production of specific cytokines, including IL-4, IL-5, and IL-13, which are key to their function in promoting B cell activation and class switching.
2. The activation of Th2 cells occurs upon recognition of antigens presented by dendritic cells in the context of major histocompatibility complex (MHC) class II molecules.
3. Th2 responses are crucial for fighting off helminth infections, as they facilitate the expulsion of these parasites through mechanisms like mucus secretion and eosinophil recruitment.
4. An imbalance favoring Th2 responses over Th1 responses can lead to allergic diseases, such as asthma, hay fever, and eczema, due to excessive IgE production and eosinophil activation.
5. Research indicates that certain environmental factors and genetic predispositions can influence the differentiation of naive T cells into the Th2 phenotype, impacting individual susceptibility to allergies.

Review Questions

• How do Th2 cells contribute to the activation of B cells during an adaptive immune response?
  • Th2 cells contribute to B cell activation by releasing specific cytokines such as IL-4 and IL-5. These cytokines stimulate B cells to proliferate and differentiate into plasma cells that produce antibodies. Furthermore, IL-4 induces class switching in B cells to produce IgE, which is crucial for combating parasitic infections and mediating allergic reactions.
• Discuss the role of cytokines produced by Th2 cells and how they affect other immune cells in the context of an allergic reaction.
  • Cytokines produced by Th2 cells, like IL-4 and IL-13, play pivotal roles in promoting an allergic response. These cytokines enhance the recruitment and activation of eosinophils and mast cells. Eosinophils contribute to inflammation and tissue damage during allergic reactions, while mast cells release histamine and other mediators that drive symptoms such as itching and swelling. This cascade highlights how Th2-derived cytokines modulate the immune landscape during allergic responses.
• Evaluate the implications of an exaggerated Th2 response on public health, particularly regarding allergy prevalence.
  • An exaggerated Th2 response has significant public health implications as it contributes to the rising prevalence of allergic diseases globally. Factors like urbanization and changes in lifestyle may increase susceptibility by skewing immune responses towards Th2 dominance. This leads to higher rates of conditions such as asthma, allergic rhinitis, and eczema, creating challenges for healthcare systems. Understanding this dynamic is essential for developing effective prevention strategies and therapies aimed at restoring balance within the immune system.

Related terms

Cytokines:

Signaling molecules released by Th2 cells that mediate and regulate immunity, inflammation, and hematopoiesis.

B cells:

A type of white blood cell that is crucial for the humoral immune response, producing antibodies in response to antigens.

IgE:

Immunoglobulin E is an antibody associated with allergic reactions and responses to parasitic infections, produced predominantly in Th2-mediated immune responses.