From: Reuters
Published November 19, 2007 07:26 PM

New research explains why some tumors undetected

By Michael Kahn

LONDON (Reuters) - Researchers looking at immune systems in healthy people have discovered an interaction between two types of cells that may help explain why the body's natural defenses fail to detect and fight tumors.

The findings could lead to better cancer treatments and new targets for drugs, said Leonie Taams, an immunologist at King's College London, who led the study published on Tuesday.

The study looked at regulatory T-cells, which keep the immune system stable and are key in controlling immune cells called macrophages that cause inflammation. Inflammation is one of the body's first responses when fighting infection.

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Taams said the study showed that just as regulatory "police officer" T-cells can stop killer T-cells from attacking a tumor, they can also shut off macrophages, suppressing inflammation and keeping the body from detecting tumors.

"Before these police officers were never believed to speak to these macrophages. We have shown they can do it," Taams said in a telephone interview.

"The regulatory T-cells trick the immune system into thinking there is no problem."

Scientists had known things like the presence of bacteria typically activated macrophages but understood less about what caused the cells to switch off.

Taams said the study -- in which researchers took macrophages from healthy people and cultured them in dishes either on their own, with normal T-cells or with regulatory T-cells -- answered that question for the first time.

Their findings, published in the Proceedings of the National Academy of Sciences, could lead to better ways to detect whether someone's immune system is fighting a tumor after treatment, she said.

It could also lead to more specific drugs aimed at removing or altering these non-inflammatory macrophages that suppress the immune system's response, Taams added.

"The work was done in healthy people but we believe it has implications for cancer," she said. "We believe that the regulatory T-cells are doing the job they are supposed to do but they are doing it at the wrong place and the wrong time."

"The findings provide more ammunition for the idea that regulatory T-cells should be removed from tumors."

(Editing by Maggie Fox and Michael Winfrey)

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