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What is true about T-lymphocytes in mammals?
A. There are three main types-cytotoxic, helper and suppressor.
B. They originate in lymphoid tissues.
C. They scavenge damaged cells and cellular debris.
D. They are produced in thyroid.

Last updated date: 18th Jun 2024
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Hint: T lymphocyte is a kind of white blood cell. They support, save the body from infection and may help fight against cancer. They are also called T-cell and thymocyte.

Complete answer:
To answer this question, first, we need to know about T- lymphocytes present in mammals. T cells (also called T lymphocytes) are one of the major components of the adaptive immune system. Their roles include directly killing infected host cells, activating other immune cells, producing cytokines and regulating the immune response.
Now, let us find the solution from the option.
T cells account for about 80% of all lymphocytes. They are named T cells because they mature in the thymus, a gland found in the chest.
There are three kinds of T cell lymphocytes:-
->Cytotoxic T cell
->Suppressor T cell
->Helper T cell.
The helper T cells are usually the most vital cells in adaptive immunity because they are needed for most adaptive immune signals. They not only assist triggered B cells to release antibodies and macrophages to damage or engulf invading microorganisms, but they also activate cytotoxic T cells to engulf contaminated target cells. A cytotoxic T cell is a kind of white blood cell which destroy infected cells that are harmed by other causes or cancer cells. The helper regulatory T cells previously called as suppressor T cells are a subdivision of T cells that control or maintain the immune system, balance tolerance to self-antigens, and inhibit autoimmune disease.

Thus, the correct option is A. i.e. There are three main types-cytotoxic, helper and suppressor.

Note:T cells originate in the bone marrow and mature in the thymus. In the thymus, T cells multiply and differentiate into helper, regulatory, or cytotoxic T cells or become memory T cells. They are then sent to peripheral tissues or circulate in the blood or lymphatic system. Once stimulated by the appropriate antigen, T cells work to maintain immune reactions, so they are also named as helper T-cells. The cytotoxic T cells are triggered by many cytokines, tie to and remove or kill cancer cells and infected cells.