Article: Immunology: Guide for a cell-fate decision
From: Robert Karl Stonjek (rstonjek_at_bigpond.net.au)
Date: 02/23/05
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Date: Wed, 23 Feb 2005 16:47:50 -0500 (EST)
Immunology: Guide for a cell-fate decision
ELLEN A. ROBEY
Ellen A. Robey is in the Department of Molecular and Cell Biology, 471 Life
Sciences Addition, University of California, Berkeley, California 94720,
USA.
e-mail: erobey@uclink.berkeley.edu
How does an immature cell know how to develop into a specialized one? A
fortunate observation has revealed one of the cues that guide precursor
immune cells to their ultimate fate.
During the development of multicellular organisms, precursor cells mature
into specialized cell types, such as muscle cells or blood cells. This
cellular differentiation must be carefully orchestrated to generate the
correct numbers and types of cells at the right time and place. Unravelling
the regulatory circuitry involved is a major goal of developmental
biologists. In a striking illustration of Louis Pasteur's famous statement,
"Chance favours only the prepared mind", a fortuitous mutation in a mouse
has led Kappes and colleagues to a breakthrough in understanding how
immune-cell precursors adopt their appropriate cell fate (He et al.1, page
826 of this issue).
In the mammalian thymus, precursor cells called thymocytes give rise to two
types of mature immune cell: CD4 helper T cells, which alert the immune
system when the body is invaded by a pathogen and coordinate an inflammatory
response; and CD8 killer T cells, which destroy cells that have been
invaded. Each T cell has receptors for a specific antigen on its surface.
The gene that encodes these receptors is rearranged during the cell's
development to produce one of a huge potential variety of receptor genes.
The range of receptors consequently produced by the entire population of
mature T cells allows the immune system to recognize virtually any pathogen.
These T cells probe other cells they come across, and respond when they find
'foreign' peptides that might signal the presence of a pathogen. The foreign
peptides become bound to molecules of the major histocompatibility complex
(MHC) and are displayed on the surface of invaded cells and other immune
cells. The MHC comes in two varieties: class I, which is recognized by the
CD8 killer T cells, and class II, which is recognized by the CD4 helper T
cells. The CD8 and CD4 proteins aid the interaction between the MHC and the
T-cell antigen receptor.
Full Text at Nature
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v433/n7028/full/433813a_fs.html
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Robert Karl Stonjek
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