Social stress may cause severe damage.

• Position: Immune System - Bacterial infection research - Brief Article

Certain social interactions may weaken the immune system to the point it can't control inflammation, suggests research at Ohio State University, Columbus. In turn, the inflammation may cause irreversible organ and tissue damage. In the study, socially stressed mice were twice as likely to die after exposure to a compound that triggered an infection-like response as physically stressed mice were. "The stress somehow triggered an abnormal immune response to a bacterial toxin," indicates John Sheridan, professor of molecular virology.

For reasons researchers don't fully understand, social stress intensified the immune system's response to a compound called lipopolysaccharide (LPS), which stimulates immune cells to react as if they were fighting an infection. In the mice, the response triggered the overproduction of proinflammatory cytokines, hormones that are responsible for regulating immune function. This sudden onslaught of inflammatory cytokines caused toxic shock--similar to septic shock in humans--in most of the socially stressed mice. Yet, the animals remained healthy until they were injected with LPS. The physically stressed mice didn't have the same level of inflammation after LPS exposure.

"Cytokines are strong weapons for killing bacteria," Sheridan points out. "But they're a double-edged sword. While we need them for everything...