Connective tissue-degrading enzymes of human leukocytes

Human leukocytes, when exposed to aggregated human gamma-globulin (AHGG) or immune complexes (isolated from RA synovial fluid) fixed to a cartilagenous surface, release neutral proteases that degrade the extracellular matrix of cartilage. The chondromucoprotein destruction by these proteases is suppressed by a variety of synovial fluids but is not susceptible to inhibition by trypsin, chymotrypsin, elastase inhibitors, or a combination of these agents. The inhibitory effect of synovial fluid can be reversed in the presence of increasing enzyme concentrations. Intact viable human polymorphonuclear leukocytes in the presence of AHGG also release a collagenase precursor that can be activated by limited proteolysis with trypsin or RA synovial fluids. Enzyme release (neutral proteases) by phagocytosing cells is inhibited by the antiinflammatory agents phenylbutazone and colchicine; these agents do not affect release of the collagenase precursor. However, the latent collagenase release is susceptible to inhibition when leukocytes are preincubated (prior to exposure to AHGG) with inhibitors of protein synthesis. Under these conditions, neutral protease release is unaffected.