T cell
T cell
A T cell or T lymphocyte is a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called T cells because they mature in the thymus from thymocytes (hence T cell).
Types of T cells[edit | edit source]
There are several different types of T cells, each with a unique function:
- Helper T cells (Th cells) – they assist other white blood cells in immunologic processes, including maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells and macrophages.
- Cytotoxic T cells (Tc cells, CTLs) – they destroy virus-infected cells and tumor cells, and are also implicated in transplant rejection.
- Memory T cells – they remember antigens they have encountered in the past, allowing for a faster response to subsequent encounters.
- Regulatory T cells (Tregs) – they maintain tolerance to self-antigens and prevent autoimmune disease.
- Natural killer T cells (NKT cells) – they share characteristics of both T cells and natural killer cells.
T cell activation[edit | edit source]
T cells are activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response.
Role in disease[edit | edit source]
T cells play a key role in the immune response to many diseases, including viral infections such as HIV and autoimmune diseases like rheumatoid arthritis and type 1 diabetes. They are also a critical component of the immune response to cancer, and are a target for many new cancer therapies.
See also[edit | edit source]
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Contributors: Prab R. Tumpati, MD