Phagocytic release and activation of human leukocyte procollagenase

DESTRUCTION of collagen-containing structures occurs in those inflammatory disease states which are characterised by the infiltration of large numbers of granulocytic leukocytes¹. The degradation of collagen fibrils is probably mediated by a specific mammalian collagenase, since native collagen at physiological pH and temperature is resistant to hydrolysis by other proteolytic enzymes². Active collagenase initially identified in culture fluids of tadpole tail³ has since been demonstrated in cultures of human skin⁴, gingiva⁵, and rheumatoid synovium⁶. Furthermore, collagenase has been demonstrated in human rheumatoid synovial fluid and extracted directly from human granulocytic leukocytes^7,8. Recently, an inactive collagenase precursor was extracted from human leukocytes⁹. We now report that a collagenase precursor is liberated in large quantity from viable cells during phagocytosis of aggregated human γ globulin (AHGG). In addition, we show that the neutrophil is the principal source of this proenzyme, with only small amounts present in lymphocytes or lymphoblasts. The proenzyme can be activated by trypsin or rheumatoid synovial fluids but not by osteoarthritic synovial fluid.