A type of white blood cell that is of key importance to the immune system and is at the core of adaptive immunity, the system that tailors the body’s immune response to specific pathogens. The T cells are like soldiers who search out and destroy the targeted invaders.
Immature T cells (termed T-stem cells) migrate to the thymus gland in the neck, where they mature and differentiate into various types of mature T cells and become active in the immune system in response to a hormone called thymosin and other factors. T-cells that are potentially activated against the body’s own tissues are normally killed or changed (“down-regulated”) during this maturational process.
There are several different types of mature T cells. Not all of their functions are known. T cells can produce substances called cytokines such as the interleukins which further stimulate the immune response. T-cell activation is measured as a way to assess the health of patients with HIV/AIDS and less frequently in other disorders.
T cell are also known as T lymphocytes. The “T” stands for “thymus” — the organ in which these cells mature. As opposed to B cells which mature in the bone marrow.
- T (thymine)
In genetics, T stands for thymine, one member of the A-T (adenine-thymine) base pair in DNA. The other base pair in DNA is G-C (guanine-cytosine). Each base pair forms a “rung of the DNA ladder.” A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a […]
- Td immunization
Td is the vaccine given to children over six and adults as a booster for immunity to diphtheria and tetanus.
A drop of the salty secretion of the lacrimal glands which serves to moisten the conjunctiva and cornea.
- Tear film
The liquid layer bathing the cornea and conjunctiva. It creates a perfectly smooth liquid outer layer that polishes the corneal surface, mechanically traps and flushes out foreign bodies and chemicals, contains bacteriostatic substances that inhibit the growth of microorganisms, and reduces the surface friction associated with eyelid blinking and eye movement.
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Riot control agent poisoning.