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.
There are many groups of people who would not necessarily answer the phone, including addicts who are out looking for drugs, as well as business people out for a two-martini lunch. The survey crew calls people they don't know and asks them if anyone in their household has committed a felony (used drugs) recently.