Several biological systems such as the complement cascade and the clotting systems are controlled by complex protease-protease inhibitor systems. The objective of this research proposal is to investigate the role of such protease and protease inhibitor systems in the regulation of lymphocyte functions. This includes regulation of proliferation as well as differentiated functions. The approach to the problem will be multi-faceted. First, using short-term culture and various mitogenic stimuli, the ability of natural and synthesized protease inhibitors will be tested for their ability to interfere with proliferation of subpopulations of lymphoid cells. This aspect of the research will concentrate on alpha2-macroglobulin which we have shown to possibly be a regulatory molecule. Secondly, in addition to proliferation, the role of proteases and protease inhibitors in lymphocyte functions such as development of antibody secreting cells (primary and secondary cultures) and cytotoxicity will be investigated. Thirdly, the cell-surface modifications induced by proteolytic activation of lymphoid cells will be investigated biochemically using cell-surface iodination techniques. Fourthly, the biochemical nature of cell-surface proteases, which we and others have shown to occur on lymphoid cells, will be determined. The cell surface proteases on subpopulations of lymphoid cells will be characterized for substrate specificity, activity during lymphocyte activation, molecular weight and antigenic nature. Results obtained from the proposed research will provide information on internal immunological regulation (T-cell-B-cell, B-cell-macrophage, etc.) as well as on the nature of possible immunological modifications induced by interaction with the environment under homeostatic conditions or in pathological conditions such as autoimmune disease states (arthritis) or cancer.