Researchers use chemical from medicinal plants to...( Like other kinds of cells immune cel...)

Like other kinds of cells, immune cells lose the ability to divide as they age because a part of their chromosomes known as a telomere becomes progressively shorter with cell division. As a result, the cell changes in many ways, and its disease fighting ability is compromised.

But a new UCLA AIDS Institute study has found that a chemical from the Astragalus root, frequently used in Chinese herbal therapy, can prevent or slow this progressive telomere shortening, which could make it a key weapon in the fight against HIV.

"This has the potential to be either added to or possibly even replace the HAART (highly active antiretroviral therapy), which is not tolerated well by some patients and is also costly," said study co-author Rita Effros, a professor of pathology and laboratory medicine at the David Geffen School of Medicine at UCLA and member of the UCLA AIDS Institute.

The study, to be published in the Nov. 15 print edition of the Journal of Immunology, is available online at http://www.jimmunol.org/cgi/content/full/181/10/7400.

A telomere is a region at the end of every cell chromosome that contains repeated DNA sequences but no genes; telomeres act to protect the ends of the chromosomes and prevent them from fusing together rather like the plastic tips that keep shoelaces from unraveling. Each time a cell divides, the telomeres get shorter, eventually causing the cell to reach a stage called replicative senescence, when it can no longer divide. This seems to indicate that the cell has reached an end stage, but, in fact, the cell has changed into one with new genetic and functional characteristics.

A great deal of cell division must take place within the immune system for the system to function properly. For example, the so-called "killer" CD8 T-cells that help fight infection have unique receptors for particular antigens. When
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