May 7, 2007 / 5:06 PM / in 12 years

Indian scientists identify troublemaker TB protein

HONG KONG (Reuters) - Researchers in India have identified a protein in the tuberculosis bacteria which weakens the body’s immune response to the deadly disease.

By knowing what the TB protein can do, the scientists hope to find another cure for treating the disease. The protein may also be harnessed to stop diseases which are caused by inflammation going out of control, such as hay fever, rheumatoid arthritis and atherosclerosis.

Writing in the latest issue of the journal Nature Immunology, the scientists said the protein, ESAT-6, binds itself to a type of white blood cells and disrupts their ability to fight off harmful viruses and bacteria.

More than a third of the world’s population is infected with TB and the infection rate is one every second. However, only one in 10 infected persons will develop symptoms and that usually happens when their immune systems are weak.

Left untreated, TB, or Mycobacterium tuberculosis, kills half its victims.

Lead researcher Joyoti Basu at the Bose Institute in Calcutta said the ESAT-6 protein in TB bacteria latches onto certain receptors called TLR2 on the surface of macrophages — a type of white blood cell.

When that happens, the macrophages can’t function properly.

“Then the white blood cells would not be able to put up as good a fight,” she said in a telephone interview.

Macrophages are important “sentry cells” in our immune system. They engulf and digest invaders like viruses and bacteria, and stimulate other immune cells to fight the invaders.

Basu’s team created mice without TLR2 receptors on their macrophages. The scientists then extracted the macrophages and exposed the cells to TB bacteria.

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