An immune cell swallows a small capsule-shaped bacteria. The immune cells which help protect us from disease does not generally work the way they should in space travellers and it could be something to do with their shape. Researchers at NASA's Johnson Space Center (JSC) have been studying how immune cells behave in microgravity as part of their research on the health effects of space on astronauts.
It has been found that astronauts have elevated virus levels their sneezes contain up to ten times more Epstein-Barr virus than normal Earth sneezes, for example. Looking at the key immune cells, researchers have found that B-cells, which produce antibodies to flag invading micro-organisms for destruction, and T-cells which actually physically attack them, have both been found to behave differently in space.
In space, T-cells do not multiply properly, neither move or signal each other as well and overall seem less able to destroy invaders. While one possibility is that the unique physical and psychological stresses of space flight might trigger immune-altering hormones, another possibility is that the weightlessness of space might be affecting the immune cells directly. To investigate this, NASA has developed a "rotating bioreactor" which allows researchers to investigate the possible effects of microgravity on individual immune cells without the complications of hormone effects.
The bioreactor consists of a rotating container full of a fluid which allows cells to remain suspended for months at a time in continual free fall, just as they would be in Earth orbit. According to Neal Pellis, chief of JSC's Biological systems Office, the cells in the bioreactor began to change in the first 15 minutes. One of the first changes was that T-cells were somehow forced to remain round and the researchers believe this could be responsible for the problems seen.
On Earth, T-cells can change their shape, protruding portions of themselves so they can move around like amoebas. T-cells need to move in order to get to sites of infections, tumors and immune system organs. The changed shape could also make it harder for cells to communicate as their ability to interact is reduced by the rigid round shape. Researchers do not understand why the T-cells stay round in microgravity but suggest that intermolecular or submolecular forces such as hydrogen bonding might play a larger role in determining the cell's shape in the absence of Earth's gravity.
They say finding out is important to both astronauts and people on Earth since understanding the way physical forces affect T-cells could eventually enable scientists to control them. "There are times when we don't want them to invade - transplants, for example. And there are cases when we want them to act vigorously, like in tumors," said Pellis.