: any of several lymphocytes (such as a helper T cell) that differentiate in the thymus, possess highly specific cell-surface antigen receptors, and include some that control the initiation or suppression of cell-mediated and humoral immunity (as by the regulation of T and B cell maturation and proliferation) and others that lyse antigen-bearing cells : t lymphocyte
The immature lymphoid cell, in turn, can be processed into a B cell, which makes infection-fighting antibodies, or a T cell, which recognizes foreign tissue and virally infected cells and directs the activities of the rest of the immune system.—Gina Kolata
T cells recognize antigen only in association with cell surface molecules encoded by the major histocompatibility complex …—Miranda Robertson
see helper t cell, killer t cell compare b cell
: any of several lymphocytes (such as a helper T cell) that differentiate in the thymus, possess highly specific cell-surface antigen receptors, and include some that control the initiation or suppression of cell-mediated and humoral immunity (as by the regulation of T and B cell maturation and proliferation) and others that lyse antigen-bearing cells : t cell
T lymphocytes differentiate in the thymus and interact directly with other cells to regulate the immune response or to kill cells expressing the appropriate antigen.—Alan F. Williams
Activation of a T lymphocyte requires occupancy of its antigen-specific cell surface receptor … by its appropriate ligand (processed antigen presented by class I or class II MHC molecules) and a second signal from a growth factor.—Suryaprakash R. Sambhara et al.
compare b lymphocyte
Cite this Entry
“T cell.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/T%20cell. Accessed 1 Aug. 2026.
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