Cd4+ t cells
CD4+ T cells, also known as T helper cells, are a type of lymphocyte that play a crucial role in the immune system. They are a subset of T cells that express the CD4 glycoprotein on their surface. CD4+ T cells are essential for orchestrating the immune response by activating and directing other immune cells, including B cells, CD8+ T cells, and macrophages.
Function[edit | edit source]
CD4+ T cells are primarily involved in the adaptive immune response. They recognize antigens presented by antigen-presenting cells (APCs) in the context of Major Histocompatibility Complex (MHC) class II molecules. Upon activation, CD4+ T cells differentiate into various subsets, including:
- T helper 1 (Th1) cells: These cells are involved in the response against intracellular pathogens such as viruses and certain bacteria. They produce cytokines like interferon gamma (IFN-γ) that activate macrophages and enhance the killing of intracellular pathogens.
- T helper 2 (Th2) cells: These cells are important for the response against extracellular parasites, such as helminths. They produce cytokines like interleukin 4 (IL-4), IL-5, and IL-13, which help in the activation of B cells and the production of antibodies.
- T helper 17 (Th17) cells: These cells are involved in the defense against extracellular bacteria and fungi. They produce IL-17 and other cytokines that recruit neutrophils and other immune cells to sites of infection.
- Regulatory T (Treg) cells: These cells help maintain immune tolerance and prevent autoimmune diseases by suppressing the activation of other immune cells.
Role in Disease[edit | edit source]
CD4+ T cells are implicated in various diseases. In HIV/AIDS, the virus specifically targets and depletes CD4+ T cells, leading to immunodeficiency. In autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, dysregulated CD4+ T cell responses contribute to tissue damage.
Clinical Significance[edit | edit source]
The CD4 count is a critical marker used to assess the immune function in individuals with HIV. A low CD4 count indicates a weakened immune system and a higher risk of opportunistic infections.
Also see[edit | edit source]
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