A PLASMIN-SPLIT FRAGMENT OF C'3 AS A NEW CHEMOTACTIC FACTOR

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Abstract
When strepto-kinase and highly purified human plasminogen are added to human serum or to partly purified or highly purified preparations containing the 3rd component of complement (C[image]3), either rabbit or human, or chemotactic factor is generated. This chemotactic factor is a split product of C[image]3 and is dialyzable, fast moving electrophoretically, slowly sedimenting in sucrose density gradient ultracentrifugation, and has an approximate molecular weight of 6000. This fragment accounts for approximately 4% of the intact molecule. The C[image]3 fragment has the following biologic properties It is chemotactic for rabbit PMN'' s [polymorphonucleocytes] in vitro, it causes accumulation of PMNs in vivo, and it increases vascular permeability in rat skin. In addition to generating a chemotactic factor, plasmin destroys the complement-associated chemotactic factor that is a trimolecular complex consisting of the 5th (C[image]5), 6th (C[image]6), and 7th ([image]C7) components of complement. This was shown by a loss of chemotactic activity, as well as a dissociation of the C[image]5, C[image]6, C7 complex and a destruction of C[image]6 hemolytic activity. The biologic significance of the plasmin-generated chemotactic factor is discussed in relation to other recently discovered biologically active fragments of C[image]3.