From the Guidelines
A Th2 cell is a type of helper T lymphocyte that plays a crucial role in the immune system's response to parasites, allergens, and certain pathogens, characterized by the production of cytokines such as IL-4, IL-5, IL-13, and IL-10, which promote antibody production and eosinophil activation. These cells develop from naive CD4+ T cells when exposed to specific cytokines like IL-4 and IL-2 1. The most recent evidence suggests that IL-4 is a major differentiation factor driving a TH2 type response by initiating T cell differentiation toward the TH2 subtype, and it also induces the production of type 2 associated cytokine and chemokines such as IL-5, IL-9, IL-13, TARC, and eotaxin 1. Th2 cells are particularly important in fighting helminth (worm) infections by promoting IgE antibody production by B cells and activating eosinophils to attack these parasites. However, excessive Th2 responses are also responsible for allergic conditions like asthma, atopic dermatitis, and hay fever.
The development of Th2 cells involves the processing of allergens by dendritic cells expressing CD1a and CD11c, in the nasal epithelium mucosa, and subsequent presentation of allergenic peptides by MHC II molecules to T-cell receptors on resting CD4+ cells in regional lymph nodes 2. With appropriate costimulatory signals, allergen-stimulated resting T cells proliferate into T H 2-biased cells that produce IL-3, IL-4, IL-13, IL-5, GM-CSF, and other cytokines. The balance between Th2 cells and other T helper subsets (like Th1 and Th17) is critical for appropriate immune function, as imbalances can lead to either insufficient protection against certain pathogens or inappropriate inflammatory responses to harmless substances.
Key characteristics of Th2 cells include:
- Production of cytokines such as IL-4, IL-5, IL-13, and IL-10
- Promotion of antibody production and eosinophil activation
- Involvement in fighting helminth (worm) infections
- Contribution to allergic conditions like asthma, atopic dermatitis, and hay fever
- Development from naive CD4+ T cells when exposed to specific cytokines like IL-4 and IL-2 1.
From the Research
Definition and Characteristics of Th2 Cells
- Th2 cells are a type of helper T cell that plays a critical role in immune response against helminths invading cutaneous or mucosal sites 3, 4.
- They are characterized by the production of interleukin-4 (IL-4), IL-5, and IL-13 3, 5, 4.
- Th2 cells are also involved in the pathophysiology of allergic diseases such as asthma and allergic diarrhea 3, 4.
Function and Differentiation of Th2 Cells
- The differentiation of naive CD4 T cells into Th2 cells is determined by signaling pathways and key molecules 5.
- Th2 cells produce "type 2 immune response-related" cytokines, including IL-4, IL-5, and IL-13, which are critical for protective immunity against infections of extracellular parasites 5.
- Th2 cells can also undergo antigen-induced cell death, which is influenced by the antigen dose dependence of T helper differentiation 6.
Role of Th2 Cells in Immune Responses
- Th2 cells play a central role in type 2 immune responses, which are characterized by the production of IL-4, IL-5, and IL-13 5, 4.
- Th2 cells are involved in the expulsion of parasitic gastrointestinal nematodes, and IL-13 plays a unique role in this process 7.
- Th2 cells also contribute to the development of allergic diseases, such as asthma, by inducing the production of immunoglobulin E (IgE) and eosinophils 7.