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

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

The treatment programs a person’s own T cells — immune cells that usually fight infection — to identify and attack proteins found on tumor cells. —Kaitlin Sullivan, NBC News, 19 Mar. 2025

In a study published last year, Sette and his team tested blood samples collected from volunteers to identify whether their T cells that target fragments of the flu virus could do the same for H5N1 bird flu. —Will Stone, NPR, 19 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