<Tr> <Th> TH </Th> <Td> H2. 00.04. 1.02007 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terms of microanatomy (edit on Wikidata) </Td> </Tr> <P> 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 (although some also mature in the tonsils). The several subsets of T cells each have a distinct function . The majority of human T cells rearrange their alpha and beta chains on the cell receptor and are termed alpha beta T cells (αβ T cells) and are part of the adaptive immune system . Specialized gamma delta T cells, (a small minority of T cells in the human body, more frequent in ruminants), have invariant T - cell receptors with limited diversity, that can effectively present antigens to other T cells and are considered to be part of the innate immune system . </P> <P> Effector cells are the superset of all the various T cell types that actively respond immediately to a stimulus, such as co-stimulation . This includes helper, killer, regulatory, and potentially other T cell types . Memory cells are their opposite counterpart that are longer lived to target future infections as necessary . </P>

What does the t in t cell stand for
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