Inhibition of Anaphylactic Release of Vascular Permeability Factor or Histamine by Specific Protease Inhibitor in Tissue Culture

Abstract

OUR knowledge of the cellular mechanism of histamine release in anaphylaxis is imperfect; there are several controversial hypotheses^1,2. The difficulty is due partly to the lack of a specific metabolic inhibitor for the enzymatic reactions activated by the antigen–antibody reaction. By the use of cultured cells, we obtained the rapid activation of a heat-labile, specific SH-protease (Arthus protease) in the early stage of the reaction and the release of a polypeptide inhibitor of this enzyme at a later stage^3–5. The inhibitor was also isolated from skin lesions during Arthus reactions, and it was highly purified as a homogeneous substance paper-electrophoretically and by ultracentrifugation⁶. Its molecular weight was approximately 12,500 (ref. 7). It inactivated the cellular SH-protease and papain but had no effect on trypsin and α-chymotrypsin. The inactivation of the proteases by this inhibitor occurred in parallel with a decrease in the titrable SH-groups of the enzyme molecules⁸. We further obtained the release of an immediate antihistamine susceptible permeability factor (PF) and a delayed antihistamine insusceptible PF (Arthus PF)^9,10 during the anaphylactic reaction. This purified inhibitor has been used to characterize further the enzymatic mechanism of the anaphylactic release of immediate PF and histamine.