Cytokines Handout PDF

## Cytokines Defence against viruses, microorganisms and their products, parasites, and cancer cells are mediated by both nonspecific and specific immunity. Cytokines are required for immunoregulation of both of these immune responses. The term cytokine is a generic term for the soluble protein o...

## Cytokines Defence against viruses, microorganisms and their products, parasites, and cancer cells are mediated by both nonspecific and specific immunity. Cytokines are required for immunoregulation of both of these immune responses. The term cytokine is a generic term for the soluble protein or glycoprotein released by one cell population that acts as an intercellular mediator or signalling molecule. - When released from mononuclear phagocytes, these proteins are called monokines. - When released from T lymphocytes they are called lymphokines - When produced by a leukocyte and the action is on another leukocyte, they are interleukins. - If their effect is to stimulate the growth and differentiation of immature leukocytes in the bone marrow, they are called colony-stimulating factors (CSFs). Recently cytokines have been grouped into the following categories or families: chemokines, haematopoietins, interleukins, and members of the tumour necrosis factor (TNF) family. - Cytokines can affect the same cell responsible for their production (an autocrine function), nearby cells (a paracrine function), or can be distributed by the circulatory system to their target cells (an endocrine function). Their production is induced by nonspecific stimuli such as a viral, bacterial, or parasitic infection; cancer; inflammation; or the interaction between a T cell and antigen. Some cytokines also can induce the production of other cytokines. - Cytokines can activate cell proliferation and/or cell differentiation. - Cytokines can inhibit cell division and cause apoptosis (programmed cell death). Chemokines, one type of cytokine, stimulate chemotaxis and chemokinesis (i.e. they direct cell movement) and thus play an important role in the acute inflammatory response. ### Summary of cytokine types: - **Cytokines** are required for both specific and nonspecific immune responses. - **Small soluble proteins/glycoproteins** released by one cell population that act as signalling molecules. - **Monokines** are released from mononuclear phagocytes. - **Lymphokines** are released from T-lymphocytes. - **Interleukins** are procured by leukocytes and the action is on another leukocyte. - **Colony stimulating factors** stimulate growth and differentiation of leukocytes in the bone marrow.