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

The new study follows on from a breakthrough in 2022, when the team found that UA induced a biological pathway that rejuvenates the cellular power plants – mitochondria – in T cells, equipping these immune cells with more cancer-fighting might. —New Atlas, 16 Nov. 2025

Robinson said the pathway described in his study could activate that T cell response. —Aria Bendix, NBC news, 13 Nov. 2025

The drug binds to a particular protein on immune system cells called T cells and reduces their ability to attack the body’s beta cells. —Tara Haelle, Scientific American, 14 Oct. 2025

Their work revealed the existence of regulatory T cells and the FOXP3 gene, which together help maintain immune balance. —Shane Croucher, MSNBC Newsweek, 10 Oct. 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