Tuesday, May 1, 2012
In at least one common case it is apparently the latter. Aspergillus fumigatus is a very common saprotrophic fungus and its spores are everywhere. In fact its estimated that everyone breathes in several hundred Aspergillus fumigatus each day.
We know that the immune system plays a vital role in fighting off this fungus because immunosuppressed individuals are susceptible to invasive A. fumigatus infection. This can take a variety of forms but most commonly manifests as invasive pulmonary aspergillosis. If not dealt with by the innate immune system then inhaled spores germinate in the warm, moist, nutrient-rich environment of the pulmonary alveoli and can lead to chronic pulmonary infections.
We know a lot about the way that our immune system functions to control potentially lethal fungal infections like A. fumigatus - here's one recent review: Immune responses against Aspergillus fumigatus: what have we learned?