Inhibits trypsin-like serine proteinases. Irreversibly inactivates trypsin without affecting chymotrypsin. Prevents nitric oxide production by activated macrophages by interfering with transcription of the iNOS gene. Blocks cell-cell adhesion and binding of HIV-1 virus to the target cells. In macrophages, blocks nitric oxide synthase induced by interferon-g and lipopolysaccharides (EC₅₀ = 80 μM). Prevents endonucleolysis accompanying apoptotic death of HL-60 leukemia cells and normal thymocytes.