T cells

T cells or T lymphocytes are a type of white blood cell that play a central role in cell-mediated immunity. They are named after the thymus, an organ where T cells mature. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor on the cell surface.

Types of T cells

There are several different types of T cells, each with a unique function:

• Helper T cells 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 (also known as CD8+ T cells) are a type of T cell that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.

• Memory T cells are a subset of antigen-specific T cells that persist long-term after an infection has resolved.

• Regulatory T cells (also known as suppressor T cells) are crucial for the maintenance of immunological tolerance. Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative selection in the thymus.

• Natural killer T cells (NKT cells – not to be confused with natural killer cells of the innate immune system) bridge the adaptive immune system with the innate immune system.

Function

T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies). The function of T cells is to recognize specific “non-self” antigens, once they have been processed and presented by Antigen presenting cells (APCs) in the context of major histocompatibility complex (MHC). T cells cannot recognize self-antigens presented by APCs and therefore, are immune to most normal body cells because these cells cannot trigger T cells' recognition process.

See also

• Immune system
• Immune response
• Lymphocyte
• B cells

T cells Resources
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