Studies on the Inhibition of C56-Initiated Lysis (Reactive Lysis). II. C567-INH – An Inhibitor of the C567 Trimolecular Complex of Complement

摘要

We have recently described an activity in serum designated ‘INH-RL’ which inhibits C56-initiated lysis (reactive lysis) of sheep red cells and which may have a role in prevention of damage to host tissue during complement activation. This activity did not prevent either formation of C567 from C56 and C7 or consumption of C8 and C9 by these complexes. Amounts of active material which prevented C56-initiated lysis in dilute GPC-EDTA did not prevent lysis of EC567 in the same reagent; however, formation of EC567 from E, C56, and C7 was inhibited. This inhibition could not be overcome by an excess of either C56 or C7 alone, but it was overcome by an excess of both C56 and C7. Consumption of C8 and C9 by mixtures of C56 and C7 was not inhibited by amounts of active material which would prevent EC567 formation. Thus, these experiments show that this activity has its predominate effect upon preventing formation of EC567 by E and C567. This activity is distinct from previously described inhibitors of complement. Despite the observations that this activity is shared by several serum proteins, its site of action is discrete. Therefore, it is suggested that the designation C567 inhibitor (C567-INH) be used to describe this activ