a lymphocyte formed in the bone marrow from which it migrates to the thymic cortex to become an immunologically competent cell; T lymphocytes have long lifespans (months to years) and are responsible for cell-mediated immunity; T lymphocytes form rosettes with sheep erythrocytes and differentiate and divide in the presence of transforming agents (mitogens); T lymphocytes have characteristic T cell receptor-CD3 complexes as surface markers and may be further categorized by function, such as helper and cytotoxic.
Synonym(s): T cell
See Also: B lymphocyte
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