Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
Important note: Information in this article was accurate in 1997. The state of the art may have changed since the publication date.
Reuters NewMedia, Inc. - Friday October 24 5:05 AM EDT
The new substance is a chemokine -- a molecule that cells use to signal one another. Chemokines are involved in the body's response to infections, and the human immunodeficiency virus (HIV) hijacks some of their functions to invade cells.
Writing in the journal Science, Ranajit Pal of Advanced BioScience Laboratories in Kensington, Maryland, and Robert Gallo's virus team at the University of Maryland said they had named the chemokine macrophage-derived chemokine (MDC).
They said CD8 immune system cells -- the so-called suppressor T-cells that respond to invaders -- secrete a soluble compound that suppresses HIV. They purified a protein from the chemical and identified it as MDC.
Other chemokines have already been shown to suppress HIV. They include RANTES, MIP-1a and MIP-1b, and SDF-1.
Pal and Gallo said it was likely that other chemokines produced by T-cells might be found that could also suppress HIV and they might work together to cause the effects that CD8 cells have.
Earlier research has shown different versions of HIV use different chemokine receptors and thus are blocked by different factors. Receptors are the chemical doorways used to hook onto cells.
HIV strains that use the CCR5 receptor, usually found early on in infection, can be suppressed by the chemokines RANTES, MIP-1 alpha and MIP-1 beta, while those that use the CXCR4 receptors later in the infection are blocked by SDF-1.
Pal and Gallo said receptors used by MDC were found on both macrophages -- the immune cells that engulf invaders -- and dendritic cells, which produce antigens, the chemicals that flag invaders for the immune cells to attack.
This is important because these are cells that HIV attacks.
"The presence of MDC receptors on both macrophages and dendritic cells has important implications for HIV pathogenesis, given that these cells are thought to be major vehicles for primary infection," they wrote in the Science report.
They said MDC might inhibit infection of dendritic cells.
Drug companies are racing to develop compounds that act like the natural suppressors. Obviously the body's natural response is not enough to overcome HIV infection, but perhaps such drugs could give it the needed boost.
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