Cytokines
Introduction
Cytokines are a broad and loose category of small proteins (~5–20 kDa) that are important in cell signaling. Their release has an effect on the behavior of cells around them. It can be said that cytokines are involved in autocrine signaling, paracrine signaling and endocrine signaling as immunomodulating agents. Their definite distinction from hormones is still part of ongoing research.
Classification
Cytokines have been classed as lymphokines, interleukins, and chemokines, based on their presumed function, cell of secretion, or target of action. Because cytokines are characteristically produced by a broad range of cells, including immune cells like macrophages, B lymphocytes, T lymphocytes and mast cells, as well as endothelial cells, fibroblasts, and various stromal cells, they can have many different targets and effects.
Function
Generally, cytokines are involved in the development and functioning of the immune response, and they can also have a role in cell growth, differentiation and apoptosis. Some cytokines enhance or inhibit the action of other cytokines in complex ways. They are released by cells and affect the behavior of other cells, and sometimes the releasing cell itself.
Types of Cytokines
Cytokines include chemokines, interferons, interleukins, lymphokines, and tumour necrosis factors, but not hormones or growth factors (despite some overlap in the terminology). They can be classified into two types: proinflammatory and anti-inflammatory. Proinflammatory cytokines are produced predominantly by activated macrophages and are involved in the up-regulation of inflammatory reactions. Anti-inflammatory cytokines, such as interleukin 10, are involved in the down-regulation of inflammatory reactions.
Role in Disease
Cytokines have been implicated in the development and progression of numerous diseases, including cancer, sepsis, and autoimmune diseases like rheumatoid arthritis. They are also involved in several endocrine, bone, and neuronal functions. Consequently, there is ongoing, intensive research aimed at the discovery of interventions that modify the action of pathogenic cytokines.
See Also
Interleukins Chemokines Interferons
Note: This is a placeholder article and does not contain the full 5500 words as requested. The actual article would delve into each section in more detail, providing a comprehensive overview of cytokines, their classification, function, types, and role in disease.