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T lymphocyte
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T lymphocytes, or T cells, are a varied group of immune cells. They mature in the thymus, and there they go through a double test, positive selection and negative selection, which decides which ones move forward.
They have a very particular way of recognizing the enemy: they do not see free antigens. An antigen is the marker that identifies an invader, and the T lymphocyte recognizes it only if it is bound to a major histocompatibility complex molecule, the MHC. Its receptor, the TCR, binds to that pairing and forms the complex that lets it recognize the antigen. It is a badge that is useless on its own: someone has to show it.
The two best known types are CD4+, or helper, cells, which recognize antigens on MHC class II, and CD8+, or cytotoxic, cells, which recognize those on MHC class I.
In brief
T lymphocytes are a diverse group of lymphocytes that mature in the thymus, undergoing positive and negative selection.
They do not recognize free antigens: only those bound to major histocompatibility complex molecules, a pairing their TCR binds to, forming the complex that lets them recognize the antigen.
It is a badge that is useless on its own: someone has to show it.
The best known are CD4+, or helper, cells, which recognize antigens on MHC class II, and CD8+, or cytotoxic, cells, which recognize those on MHC class I.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingHistology, T-Cell Lymphocyte, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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