T-lymphocytes

T-lymphocytes or T cells are a type of white blood cell that play a central role in cell-mediated immunity. They are called T cells because they mature in the thymus from thymocytes. The abbreviation "T", in T cell, stands for thymus derived.

Types of T cells

There are several different types of T cells, each with a specific 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) – they destroy virally infected cells and tumor cells, and are also implicated in transplant rejection.

• Memory T cells – they remain long-term after an infection has resolved. They quickly expand to large numbers of effector T cells upon re-exposure to their cognate antigen, thus providing the immune system with "memory" against past infections.

• Regulatory T cells (Treg cells) – they 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) – they bridge the adaptive immune system with the innate immune system.

Function

T cells are essential for human immunity. They are capable of identifying pathogens and distinguishing them from the body's own cells. Once a pathogen is identified, T cells can stimulate the immune response or directly kill infected cells.

See also

• B cells
• Immune system
• Immunology
• Lymphocyte

T-lymphocytes Resources
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