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

Lymph nodes are where T cells and B cells encounter foreign invaders and mount a defense response. — Allison Palmer, Charlotte Observer, 29 June 2026

Lymph nodes are where T cells and B cells encounter foreign invaders and mount a defense. — Allison Palmer, Sacbee.com, 29 June 2026

Rather than overstimulating immunity, which could actually worsen allergies, reishi appears to promote regulatory T cells and tamp down excessive immune responses, which can help prevent the overproduction of histamines that drive allergy symptoms. — Samantha Agate, Kansas City Star, 26 June 2026

Mogo Farm explains that reishi promotes regulatory T cells and reduces excessive immune responses rather than overstimulating the system, which could otherwise worsen allergies. — Samantha Agate, Miami Herald, 26 June 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