Identification of a tissue kallikrein in human polymorphonuclear leucocytes

We have identified a tissue kallikrein in polymorphonuclear (PMN) leucocytes of normal human blood and bone marrow by immunocytochemistry, radioimmunoassay and enzymology. Immunoreactive tissue kallikrein was visualized in the mature neutrophil leucocytes and in immature forms such as metamyelocytes and myelocytes. No tissue kallikrein was detected in eosinophil leucocytes, lymphocytes, macrophages, megakaryocytes and platelets. So far, we have failed to observe immunoreactivity to tissue kallikrein in basophils. The presence of tissue kallikrein in extracts prepared from PMN leucocytes isolated from peripheral blood was demonstrated by immunodiffusion, dot-blotting and by radioimmunoassay. The kininogenase and amidase activity of the extracts resembled that of tissue kallikrein in being resistant to soya bean trypsin inhibitor and sensitive to trasylol. The amidase activity attributable to tissue kallikrein was completely inhibited by specific antisera.