MadSci Network: Immunology

Re: What is a cytokine and a monokine? Is erythropoitin on of these?

Date: Wed Jul 28 12:16:32 1999
Posted By: Jeffrey Dorfman, Post-doc/Fellow, immunology, national Institutes of Health
Area of science: Immunology
ID: 932562895.Im

A cytokine is a protein (generally a small one) that is used by various 
white blood cells to talk to each other. Other body cells will sometimes 
secrete cytokines; but, I generally think of a cytokine as one that is 
produced by a white blood cell or produced to communicate to a white 
blood cell and usually both.

For example, some cytokines are used to promote inflammation near an 
infected cut. These cytokines will induce white blood cells in the area to 
leave the bloodstream to fight the infection. The area will also take up fluid
(swell) mostly in order to support the immune response. Some cytokines are 
also growth factors that induce responding white blood cells to divide when
it is useful for the body to have more  of those particular white blood cells 
at a particular place.

Erythropoietin wouldy fit the more general definition of a hormone or growth
factor than the definition that I use above. The term cytokine is usually 
reserved for communication proteins of white blood cells. The distinction is 
a little bit arbitrary but useful to scientists.

Precursors of erythrocytes in the bone marrow express a receptor that 
binds erythropoietin. When this receptor binds erythropoietin, these cells 
divide more quickly and live longer and thus produce more red blood cells. 

In some ways erythropoietin is related to cytokines, particularly in that its 
receptor is similar to some cytokine receptors and also is wired into the cell 
in a similar way.

I am not familiar with the term "monokine."

Feel free to email me if you have any more questions.

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