What is TH2?
TH2, or T-helper type 2 cells, are a subset of CD4+ T-helper cells that play a crucial role in the immune system. They are primarily involved in the
humoral immune response by aiding B cells to produce antibodies. TH2 cells are characterized by their production of specific cytokines such as
IL-4,
IL-5,
IL-10, and
IL-13.
Role in Immune Response
The TH2 response is essential for defending against extracellular pathogens like helminths and certain bacteria. TH2 cells facilitate the activation and differentiation of B cells into
plasma cells that produce specific antibodies. These antibodies can neutralize pathogens and mark them for destruction by other immune cells.
TH2 and Allergic Diseases
An overactive TH2 immune response is associated with allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis. In such conditions, the excessive production of TH2 cytokines leads to an increased level of
IgE antibodies. These antibodies bind to mast cells and basophils, causing them to release histamines and other mediators that result in allergic symptoms.
Histological Identification
In histology, TH2 cells can be identified using
immunohistochemistry techniques. Specific markers such as CD4 and the cytokines they produce (like IL-4 and IL-5) can be detected with antibodies tagged with fluorescent or chromogenic labels. Under a microscope, these markers help to visualize and quantify TH2 cells within tissue samples.
TH2 in Tissue Inflammation
In the context of tissue inflammation, TH2 cells contribute to the recruitment and activation of
eosinophils, mast cells, and basophils. These cells are important in the inflammatory response and can be visualized in tissue sections stained with
Hematoxylin and Eosin (H&E) staining. Eosinophils, for instance, have a distinctive bilobed nucleus and cytoplasmic granules that stain pink with eosin.
TH2 and Autoimmune Diseases
Although TH2 cells are not typically associated with autoimmune diseases, their role cannot be entirely excluded. Some autoimmune conditions may display a skewed TH1/TH2 balance, where an inappropriate TH2 response may exacerbate the disease. However, this area requires further research to fully elucidate the implications.
Therapeutic Targeting
Given their role in allergic diseases, TH2 cells and the cytokines they produce are potential therapeutic targets. Monoclonal antibodies against IL-4, IL-5, and IL-13 are being developed and used in clinical practice to treat severe asthma and other allergic conditions. These therapies aim to reduce the TH2-mediated inflammatory response and alleviate symptoms.
