On the proteolytic inhibitory effect of human foetal and neoplastic tissues

The protease inhibitory activity of different tissues was studied with a histochemical technique using fibrin as a substrate (fibrin slide sandwich technique). Human foetal tissues, placenta, decidua and tumoural (ovarian cancers with peritoneal metastases) tissues were examined. Strong inhibitory activity was found in thymus, placenta and decidua. The inhibitory activity of liver, pancreas, adrenals, spleen and ovarian cancer was moderate, while that of myocardium and kidney cortex was only weak. No such activity was found in lung, stomach, kidney medulla or peritoneal metastases. The presence of a protease inhibitor in the thymus was hitherto unknown.