I found an article that may help a bit to explain some of this. It's funny how something as small as a dust particle can set us up for certain things the rest of our lives!
"When the immune system does not function properly, it leaves the body susceptible to an array of diseases. Allergies and hypersensitivity to certain substances are considered immune system disorders. In addition, the immune system plays a role in the rejection process of transplanted organs or tissue." Check out the rest of the article at...