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

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

To simplify, Keytruda works by lifting that shield so T cells can see the cancer again. —Allison Aubrey, NPR, 1 June 2026

Later, those mast cells split again, giving rise to red blood cells and prototypic T cells. —Mrigakshi Dixit, Interesting Engineering, 25 May 2026

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