Boost for immune systems

Australian scientists have used stem cells to grow an organ in mice critical to the immune system.

They say the technique could be used to restore the human immune system in HIV-Aids and cancer patients.

"We are very confident that this work will be able to progress to humans within the next three to five years," said Jason Gill from the Monash University Medical School in Melbourne.

Gill and fellow researcher Richard Boyd say they have discovered a "small population of cells that can generate a complete and functional thymus".

The thymus, a small lymphoid organ in the neck, is critical in generating cells vital to the immune system, including infection-fighting T-cells.

But the thymus' ability to generate T-cells is dramatically reduced by ageing, viruses, chemotherapy or genetic abnormalities.

By the time a person turns 20, his or her thymus, the only organ that produces T-cells, is down to 1 per cent functionality.

HIV-Aids patients suffer life-threatening infections because their immune system is destroyed as the deadly virus kills large numbers of T-cells.

Chemotherapy and radiation therapy also destroy large quantities of the infection-fighting cells.

"Hence the need to replace the thymus in people with the virus or undergoing chemo," said Boyd.

Gill and Boyd, whose research was published in the journal Nature Immunology, said they had grown thymus organs in several mice and believed the same could be achieved in humans as the immune systems were strikingly similar.

Boyd said they had discovered that epithelium stem cells injected into mice attracted haemopoetic stem cells and converted them into infection-fighting T-cells.

"Once you have those handles, the stem cells of both epithelium and the T-cells, then you can rebuild a thymus the way you want it to be," Boyd said.

"You can use gene therapy to make the whole thing resistant to HIV infection - we may even be able to make a thymus that is resistant to chemotherapy."

Boyd said the thymus, about the size of a fingernail or pea, was grown in mice by simply injecting the epithelium stem cells under the skin.

Once a thymus was grown it could be transplanted into position, he said.

Thymus transplants have so far had limited success because they are invariably rejected by the recipient.

- REUTERS

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