Procoagulant induction by human lymphokine and interferon γ/PMA on a myelomonocytic cell line, RC2a

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Abstract
The human myelomonocytic cell line RC2a expressed procoagulant activity following stimulation with human lymphokine (LK) prepared by stimulating peripheral blood mononuclear cells with either mitogens (Concanavalin A, phytohaemagglutinin or antigen (tuberculin). Induction was rapid, with optimal activity observed between 6 and 8 h, was decreased in cultures containing serum and was not inhibited by actinomycin D or cycloheximide. The LK activity was not inhibited by an anti-interferon .gamma. (IFN.gamma.) antibody. IFN.gamma. and phorbol myristate acetate (PMA) had no activity but acted in synergy to induce procoagulant expression; interferon .alpha. plus PMA were without effect. In contrast to the LK-induced response, procoagulant induced by IFN.gamma./PMA was not detected for up to 8 h and steadily rose over 24-48 h culture and was dependent on new protein and RNA synthesis. Bacterial lipopolysaccharide, a potent inducer of thromboplastin on normal human monocytes, failed, either alone or in combination with LK, IFN.gamma., PMA or IFN.gamma. plus PMA, to activate procoagulant expression on RC2 cells. Both LK and IFN.gamma./PMA-induced procoagulant had properties of thromboplastin expressed both intracellularly and on intact, viable cells. This study shows that RC2a cells are responsive to factors produce as the result of an activated cell-mediated immune response which may therefore contribute to the coagulopathies common to this form of malignancy.