The complement activation product C5a prevents heart cells from contracting, according to Niederbichler and colleagues on page 53. This finding may help explain the cardiac dysfunction commonly seen in patients with septic shock—a disease caused by bacterial infections that is characterized in part by the robust activation of the complement system.
A central component of septic shock is decreased heart function, which deprives tissues of oxygen and nutrients and can progress to fatal multiorgan failure. Past studies have shown that a “myocardial depressant factor” is released into the serum during sepsis, with most studies attributing the depressant activity to proinflammatory cytokines released by immune cells responding to the infection.
Robust activation of the complement cascade is another hallmark of bacterial sepsis. Complement is a series of plasma proteins that helps destroy infecting microbes and attracts immune cells to sites of infection. C5a activates immune...
