Studies on the relation between the fifth component of complement and anaphylatoxinogen

摘要

AbstractPreparations of anaphylatoxinogen obtained from rat serum contain the fifth component of complement in an hemolytically active state. Conversely, crude C5 preparations of hog serum release anaphylatoxin (AT) on incubation with the AT‐forming cobra enzyme. The ratio between the C5 content and the amount of anaphylatoxinogen does not remain constant during the preparation of anaphylatoxinogen.By incubation of rat plasma with zymosan, consumption of C5 and production of AT proceed simultaneously.When instead of zymosan, aggregated human γ‐globulin is used as complementbinding agent, the two processes can be differentiated. Though a considerable portion of C5 is inactivated, only a small amount of AT is formed. Subsequent incubation with zymosan releases the full amount of AT.During incubation of hog serum with labeled guinea pig C5 and yeast,i. e.under classical conditions of AT formation in serum by contact activation, a labeled basic peptide is cleaved from the added C5. Its behavior on chromatography is rather similar to but not entirely identical with hog serum AT. Probably the same split product is obtained by treatment of labeled C5 with the cobra enzyme.It is concluded that (1) C5 appears to be the precursor of AT,i.e.anaphylatoxinogen, (2) the hemolytic activity of C5 is not essential for the release of the AT moiety and (3) the process of AT release is only partially identical with the reaction of utilization of C5 in immune hemol