Death by stress: natural IgM-induced apoptosis.

Stress kills and hence should be avoided. On the other hand, stress induction can be used to remove malignant cells by inducing cellular suicide. Natural IgM antibodies act as first-line defense in immune surveillance. These antibodies selectively kill aberrant cells by using different apoptotic stress mechanisms. They can be isolated from patients but also from healthy donors by using the human hybridoma technology. They are components of the innate immunity, and, on the basis of specific screening methods, should also be detectable in any other individual. The three tumor-specific, apoptosis-inducing natural IgM antibodies described in this review are good examples for stress-induced apoptosis and nature's resourceful ways to fight malignant growth.