Induction of procoagulant activity on human endothelial cells by Streptococcus pneumoniae

The inflammatory response in infection caused by gram-negative organisms involves induction of procoagulant activity (PCA) on human endothelial cells. Although infections caused by gram-positive organisms are also associated with fibrin formation and thrombosis, the bacterial determinants inducing PCA are unknown. This study shows that intact pneumococci and the pneumococcal cell wall efficiently induce PCA on human endothelial cells. Upon exposure of endothelial cells to pneumococci, PCA was first detectable at 30 min, peaked at 2 h, and disappeared by 6 h. The specific activities of encapsulated and unencapsulated strains for induction of PCA were equivalent. Purified pneumococcal cell walls were as potent as endotoxin in induction of PCA. The ability to induce a procoagulant state on endothelial cells is a new biological activity of gram-positive cell walls which promotes the participation of the coagulation cascade in the inflammatory response to disease caused by gram-positive organisms.