Scientists crack immune system secret

They have discovered the mechanism by which the body attempts to maintain numbers of a vital type of immune system cell at healthy levels.

The work was carried out on patients with HIV, but could also have important implications for other people - for instance cancer patients - whose immune system is weakened or destroyed.

A team from the Gladstone Institute of Virology and Immunology in California were looking for factors that regulate the level of T-cells in the body.

T-cells are disease fighting white blood cells that play a central role in the capacity of the immune system to fight off harmful invaders.

Infection with HIV destroys T-cells and decreases their T-cell production.

This leads to a serious weakening of the immune system, leaving the body vulnerable to disease and other infections.

Crucial chemical

The researchers found that a chemical called interleukin-7 (IL-7) appears to play a crucial role regulating numbers of T-cells.

IL-7 stimulates the production and expansion of T-cells.

The researchers found that IL-7 levels rise in HIV patients after the virus has begun to kill off T-cells.

They believe this is the body's way of trying to restore T-cells to their proper level.

It appears cells within the lymph nodes of the immune system are able to detect a drop in T-cell levels, and to respond by stimulating IL-7 production.

The researchers hope it will be possible to increase T-cell numbers in patients with weakened immune systems by boosting their IL-7 levels artificially.

Other types of immune restoration therapies are currently being investigated.

But the use of IL-7 may prove to be a more potent weapon against the effects of disease.

The researchers believe it has the potential to restore types of T-cells that have been completely obliterated by disease.

Other therapies can only boost overall numbers of T-cells by stimulating production of the forms of the cell that remain after the ravages of disease have taken effect.

The researchers warn that IL-7 may pose problems if administered as a therapy for HIV patients as it can also increase the replication of the HIV virus.

It may be possible to control this side effect by using other drugs.

The research is published in the journal Nature Medicine.