A Neutrophil Chemotactic Factor Derived from C′5 upon Interaction of Guinea Pig Serum with Endotoxin

Abstract

Upon activation of the complement system in guinea pig serum by endotoxin, a factor chemotactic for polymorphonuclear leukocytes is generated. This chemotactic factor has an approximate molecular weight (M.W.) of 15,000 and is independent of three minor chemotactic factors (M.W. τ;150,000, ∼68,000 and 125I C′3 or ¹²⁵I C′5. Gel filtration elution profiles of the reaction mixtures revealed that both C′3 and C′5 were cleaved in endotoxin-treated serum. Moreover, the 15,000 M.W. chemotactic factor was identified with a cleavage product of C′5 but not of C′3. In addition, rabbit anti-guinea pig C′5, but not anti-C′3, significantly inhibited the activity of the 15,000 M. W. chemotactic factor. We conclude that the majority of chemotactic activity found in whole guinea pig serum after interaction with endotoxin is a product cleaved from C′5.