Tuberculosis guarded by stem cells7th December 2010
Stem cells protect the tuberculosis (TB) bacterium from destruction, according to a recent Indian study.
The researchers found that the reason why tuberculosis patients live so long with their disease has to do with the bacterium's own self-protection mechanisms.
Theoretically, the human immune system should be well equipped to handle TB, because human T-cells can learn how to destroy bacteria and other microscopic invaders.
In practice, people who have TB live with the disease for their whole lives, often dying protracted deaths.
A third of the world's population is infected with Mycobacterium tuberculosis.
The researchers found that the reason why the body's immune system rarely learns to cope with TB has to do with stem cells.
Somehow, TB tricks the body into sending its own mesenchymal stem cells (MSC) to infection sites, nullifying the effect of T-cells.
MSC can be seen as 'master stem cells' that can turn into many different types of cell, including bone.
Gobardhan Das, staff scientist at the International Center for Genetic Engineering and Biology in New Delhi, said the bodies of TB sufferers recruited MSC to infection sites, and that the cells eventually made barriers as a result.
The Indian researchers arrived at their results by infecting mice with the disease and watching as it developed.
After the disease had spread through the bodies of the mice, the researchers extracted lung and spleen tissue.
The researchers also extracted tissue from human patients who had TB.
There was MSC at every site where the researchers also found TB.
Das said that the MSC produced nitric oxide (NO), a gas, in order to attack TB, but that the amount of NO produced did not manage to kill all of the bacteria.
The gas is found in abundance in mammalian bodies, where it acts as a signalling pathway.
It is also an air pollutant, produced by automobile engines and power plants, and is frequently used in chemical processes.
Das said that the gas also activated T-cells, and that the MSC ultimately worked against both the body and the TB bacteria, establishing an equilibrium between both.
He said that the stalemate-like nature of TB infection was what allowed it to persist as an incubatory process for entire lifetimes in a sizeable chunk of the world's population.
While most people's TB infections are completely asymptomatic and non-contagious, about 10% of all people infected with Mycobacterium tuberculosis will become sick with an active TB infection at some point in their lifetime.
The only way to avoid becoming actively infected is to maintain a consistently strong immune system.
Das said that the MSC involved in tuberculosis infection created a nest-like microenvironment for the bacteria, and that if there were any way to prevent MSC from being actively deployed in the first place, there would be no nest.
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