The cell biology of leukocyte-mediated proteolysis

Leukocyte-derived proteinases have the capacity to degrade every component of the extracellular matrix, and thereby play fundamental roles in physiolo gical processes. However, if the activity of these proteinases is uncontrol led or dysregulated, they have the capacity to contribute to tissue injury that potentially affects every organ in the body. Although there is a subst antial literature on structure and activity of these proteinases when they are free inn solution, until recently there has been little information abo ut the cell biology of proteinases and their inhibitors, Recent studies, ho wever, have identified several mechanisms by which inflammatory cells can d egrade extracellular proteins in a milieu that contains high-affinity prote inase inhibitors.