Growth Factors Versus Cytokines
Growth factor is sometimes used interchangeably among scientists with the term cytokine. Historically, cytokines were associated with hematopoietic (blood forming) cells and immune system cells (e.g., lymphocytes and tissue cells from spleen, thymus, and lymph nodes). For the circulatory system and bone marrow in which cells can occur in a liquid suspension and not bound up in solid tissue, it makes sense for them to communicate by soluble, circulating protein molecules. However, as different lines of research converged, it became clear that some of the same signaling proteins the hematopoietic and immune systems used were also being used by all sorts of other cells and tissues, during development and in the mature organism.
While growth factor implies a positive effect on cell division, cytokine is a neutral term with respect to whether a molecule affects proliferation. While some cytokines can be growth factors, such as G-CSF and GM-CSF, others have an inhibitory effect on cell growth or proliferation. Some cytokines, such as Fas ligand, are used as "death" signals; they cause target cells to undergo programmed cell death or apoptosis.
Read more about this topic: Growth Factor
Famous quotes containing the words growth and/or factors:
“The risk for a woman who considers her helpless children her “job” is that the children’s growth toward self-sufficiency may be experienced as a refutation of the mother’s indispensability, and she may unconsciously sabotage their growth as a result.”
—Letty Cottin Pogrebin (20th century)
“The economic dependence of woman and her apparently indestructible illusion that marriage will release her from loneliness and work and worry are potent factors in immunizing her from common sense in dealing with men at work.”
—Mary Barnett Gilson (1877–?)