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• T cell
  T cell

  noun

  any of several closely related lymphocytes, developed in the thymus, that circulate in the blood and lymph and orchestrate the immune system's response to infected or malignant cells, either by lymphokine secretions or by direct contact: helper T cells recognize foreign antigen on the surfaces of other cells, then they stimulate B cells to produce antibody and signal killer T cells to destroy the antigen-displaying cells; subsequently suppressor T cells return the immune system to normal by inactivating the B cells and killer T cells.
• T-cell
  T-cell

  noun

  another name for T-lymphocyte

T cell

American  

noun

Immunology.

1. any of several closely related lymphocytes, developed in the thymus, that circulate in the blood and lymph and orchestrate the immune system's response to infected or malignant cells, either by lymphokine secretions or by direct contact: helper T cells recognize foreign antigen on the surfaces of other cells, then they stimulate B cells to produce antibody and signal killer T cells to destroy the antigen-displaying cells; subsequently suppressor T cells return the immune system to normal by inactivating the B cells and killer T cells.

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T-cell British  

noun

1. another name for T-lymphocyte

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T cell Scientific  

1. Any of the lymphocytes that develop in the thymus gland and that act in the immune system by binding antigens to receptors on the surface of their cells in what is called the cell-mediated immune response. T cells are also involved in the regulation of the function of B cells.

2. Also called T lymphocyte

3. See more at cell-mediated immune response Compare B cell

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T-cell Cultural  

1. Key to the immune system, these cells originate in the bone marrow but mature in the thymus (the t stands for thymus). T-cells attack other body cells that are infected by some bacteria, a virus, or another pathogen. (Compare B-cell.)

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Discover More

T-cell counts are used as a diagnostic test to indicate the strength of the immune system in AIDS patients.

The HIV/AIDS virus destroys a type of T-cell, leading to the syndrome characterized by a defective immune system.

Etymology

Origin of T cell

1965–70; T(hymus-derived)

Example Sentences

According to the researchers, these findings raise the possibility of developing therapies that better harness CD4+ T cells, particularly against tumors that have learned to evade traditional CD8+ T cell attacks.

From Science Daily • Jun. 4, 2026

Using a standard booster approach in mice, both vaccine types produced similar antiviral T cell and antibody-producing B cell responses.

From Science Daily • Mar. 17, 2026

The new formulation, currently called GLA-3M-052-LS+OVA, is designed to replicate the T cell signals that stimulate innate immune cells in the lungs.

From Science Daily • Feb. 23, 2026

The team identified the T cell signals as cytokines that activate pathogen sensing receptors called toll-like receptors on innate immune cells.

From Science Daily • Feb. 23, 2026

This shift in immune cell production boosts T cell activity and changes how immune cells interact within areas where cancer spreads.

From Science Daily • Jan. 23, 2026