: 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
Gina KolataT 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
Miranda Robertson
: 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
Alan F. WilliamsActivation 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
Suryaprakash R. Sambhara et al.Examples of T cell in a Sentence
Recent Examples on the Web
Smita S. Iyer, The Conversation, 8 June 2026
That was fixed with something called CAR-T cell therapy, an immunotherapy first invented at Penn to treat cancer.
—Stephanie Stahl, CBS News, 3 June 2026
Delthia Ricks, Discover Magazine, 27 Jan. 2010
See All Example Sentences for T cell
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Noun
Integrins are integral for viral control T cells survey the brain and spinal cord using proteins called integrins.
—Smita S. Iyer, The Conversation, 8 June 2026
That was fixed with something called CAR-T cell therapy, an immunotherapy first invented at Penn to treat cancer.
—Stephanie Stahl, CBS News, 3 June 2026
Noun
His physician, David Golde of UCLA, found a rare T lymphocyte in Moore’s blood that could be coaxed into making an immune-boosting protein.
—Delthia Ricks, Discover Magazine, 27 Jan. 2010
See All Example Sentences for T cell
Cite this Entry
“T cell.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/T%20cell. Accessed 16 Jun. 2026.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
