Cell Wars

To help solve the mystery, researchers are using a NASA-developed "rotating bioreactor," which provides a reasonable analogy of microgravity here on Earth. Neal Pellis, chief of the Biological Systems Office in the Johnson Space Centre, explains: The core of the bioreactor is a soup-can size container that spins at the leisurely rate of 14 rpm. It allows cells to remain suspended for months at a time in continual free fall. Within their fluid environment, the tumbling cells fall toward Earth as fast as they can -- just as they would in Earth orbit.

Using the bioreactor, researchers can separate the immune system from its hormonal controls. Rather than looking at the human immune system as a whole, Pellis and his colleagues can examine the possible effects of low-gravity on individual immune cells.

In the bioreactor, says Pellis, cells begin to change within the first 15 minutes. Indeed, one of the first alterations researchers observe could possibly trigger all the other effects: T-cells are somehow forced to remain round.

It's an important change. On Earth, these cells can alter their shape. They're able to protrude portions of themselves -- an ability that they use to move around, just like amoebas do. And they need to move in order to do their job: They travel to the sites of infections, where they attack germs. They move to the sites of tumours. They locomote in and out of immune system organs, such as the appendix and tonsils, where other T-cells share samples of invading pathogens.

But it's not only the ability to move that's hampered by roundness. This simple change also makes it harder for cells to communicate. Round cells, explains Pellis, find it harder to touch each other. Their ability to interact is reduced.