General immunostimulants (adjuvants) are essential for generating immunity
to many antigens. In bacterial infections, adjuvants are provided by compon
ents of the microorganism, e.g., lipopolysaccharide. However, it is unclear
what provides the adjuvant effect for immune responses that are generated
to tumors and many viruses. Here we show that cell injury and death of tumo
r or even normal cells provide a potent adjuvant effect for the stimulation
of cytotoxic T lymphocyte responses. This adjuvant activity is constitutiv
ely present in the cytoplasm of cells and is increased in the cytoplasm of
cells dying by apoptosis. The release of these components stimulates immune
responses both locally and at a distance, and provides a simple mechanism
to alert the immune system to potential danger in almost all pathological s
ituations.