Enhancement of endothelial plasminogen activator synthesis by lymphokines

Long-term cultures of pig aortic endothelial (E) cells secrete plasminogen activator (PA). When these cells were cultured with murine lymphokine(s) produced in response to antigen, mitogen, or allogeneic stimuli, there was consistently increased PA secretion by E cells. The evidence suggests that initiator of plasminogen activator (IPA) is produced by a nylon-wool--nonadherent cell, probably a T cell. The kinetics of this activation of PA suggest that the effect of IPA on E cells is considerably delayed compared with that on phagocytic cells. The significance of these findings is discussed in terms of their possible relationship to several immunopathological states.