The most important function of immune system is to defend the body from different disease causing pathogens. Whenever there is pathology in human body, immune system is activated to protect the vital tissues from harm.
The circumstances of their disappearances are all fascinating, and some, sadly, have never been found. One of the more high-profile missing persons cases of 2012 isn't actually a missing persons case at all. Katherine Jackson was reported as missing in late-July of 2012, by her nephew, Trent Jackson.
Some disappear for decades, and sources, including some inside the police, say the number of people in Britain who have been missing from family, friends and usual haunts for more than a year is at least 16,000 and could be as many as 20,000.