A recent report on research undertaken with fruit flies that have been taken up to a zero gravity laboratory in the International Space Station have show that gravity has a profound and very specific effect on aspercts of the fly immune system that beara great resemblence to that in people. High gravity tends to increase immune activity whereas low (or no) gravity tends to switch off important parts of our immune system controlled by the Tol-like receptor. These same parts of our immune system are important for our resistance to fungal infection so it is correct to say that lack of gravity reduces our ability to fight off fungal infection.
Why should a genetic mechanism have evolved to respond to gravity? After all we are unlikely to have experienced zero gravity in all of human history - and nor is anything else on earth (unless we are descended from space travellors who had no need of an immune system in space!). Understanding how this happens will give us some answers and the work mentioned above aims to dissect out the signal & control systems involved. Future space travellors are likely to need this information in order to survive long journeys. At the same time it might reveal to us new information about our antifungal immune system that will be useful on earth.