Release of proteolytic enzymes from leucocytes attached to IUDs.

The leucocytes adhering to intrauterine devices (IUDs) were predominantly mononuclear phagocytic cells (MPCs) and granulocytes. These cells released elastase and a plasminogen activator in the culture medium. The plasminogen activator was found to be immunologically identical to tissue activator, and the release pattern indicated that the activator as well as elastase were released from both MPCs and granulocytes. Thus, the results suggest the generalized conclusion that both MPCs and granulocytes release the tissue activator-type of plasminogen activator. The urokinase-type of plasminogen activator, which was detected initially in some cultures, may originate from endometrial tissue fragments adhering to the IUD. IUDs removed in the end of the menstrual phase and in the midcycle phase released more plasminogen activator than did devices removed at the proliferative and luteal phases. No such cyclic variation was found for the release of elastase.