Interleukin-10 regulates the tissue factor activity of monocytes in an in vitro model of bacterial endocarditis

Monocytes are important effector cells in the pathogenesis of bacterial end ocarditis since they provide the tissue factor that activates the coagulati on system and maintains established vegetations. Monocytes secrete cytokine s that can modulate monocyte tissue factor activity (TFA), thereby affectin g the formation and maintenance of vegetations. In this study, we show that monocytes cultured for 4 h on a Streptococcus sanguis-infected fibrin matr ic: mimicking the in vivo vegetational surface express high levels of TFA. This was accompanied by: secretion of the proinflammatory cytokines tumor n ecrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL- 1 beta. After a 24 h incubation period the anti-inflammatory. cytokine IL-1 0 could also be detected. Our data show that, whereas TNF-alpha and IL-10 h ave a minor role in the induction of IL-10 by monocytes cultured on a fibri n matrix, TNF-alpha but not IL-10 plays an important role in the induction of IL-10 by these cells. In turn, our data show that IL-10 is an important factor in the downregulation of monocyte TFA In summary, me conclude that I L-10 is an important factor in the control of monocyte TPA in endocardial v egetations.