T cell

noun

: 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

Examples of T cell in a Sentence

Recent Examples on the Web

But a new La Jolla Institute for Immunology study published recently in Nature Communications offers the first map of which parts of the chikungunya virus trigger the strongest response from the body’s disease-fighting T cells. —Noah Lyons, San Diego Union-Tribune, 7 July 2025

Researchers found cannabinoids can inhibit the production of inflammatory cytokines and promote regulatory T cells, which are crucial for maintaining immune balance. —Tribune Content Agency, Mercury News, 20 May 2025

This can be done through boosting the numbers of regulatory T cells, which suppress a particular immune response, linked to a particular autoantigen. —Juergen Eckhardt, Forbes.com, 23 Apr. 2025

Another promising approach involves a relatively new type of immunotherapy that genetically modifies immune cells called CAR T cells. —Jon Hamilton, NPR, 25 Mar. 2025

Word History

Etymology

thymus-derived cell

First Known Use

1970, in the meaning defined above

Rhymes for T cell

• bel
• belle
• cel
• dell
• dwell
• el
• ell
• fel
• fell
• gel
• gell
• jell

Kids Definition

T cell

noun

: any of the lymphocytes (as a helper T cell) that usually mature in the thymus and take an active part in immune responses compare b cell

Medical Definition

T cell

noun

: any of several lymphocytes (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

called also T lymphocyte

see cytotoxic t cell, helper t cell, suppressor t cell, t4 cell