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 of the most well-known missing people on this list vanished forever, with no trace left behind. Their bodies were never found, and friends and family were left to wonder forever what happened. Conspiracy theories about their fates, not surprisingly, run rampant.