Biological activities of C3βc, a novel neutrophil chemoattractant derived from the β-chain of rat complement C3

Biological activities of C3βc, which is a C-terminal fragment of the β-chain of rat complement C3, have been studied by in vivo and in vitro experiments. C3βc was purified as a novel neutrophil chemoattractant from the exudate of the chronic phase of rat carrageenin-induced inflammation. The purified C3βc induced neutrophil chemotaxis in vivo when C3βc was injected into the preformed air-pouch on the back of rats. C3βc transiently increased the intracellular free Ca2+ concentration of neutrophils, and enhanced the adhesion of neutrophils to fibrinogen in vitro, suggesting that C3βc has the ability to express an adhesion molecule of rat neutrophils. In addition, C3βc at low concentrations (10−10–10−11 m) stimulated rat macrophages to produce cytokine-induced neutrophil chemoattractant-2, a member of the interleukin-8 family. Furthermore, C3βc enhanced vascular permeability in vivo, which is suppressed by cyproheptadine, suggesting that C3βc may have the characteristics of an anaphylatoxin. Our results suggest that C3βc contributes to oedema formation and neutrophil accumulation at inflammatory sites in rats. BSA, bovine serum albumin CINC, cytokine-induced neutrophil chemoattractant DMEM, Dulbecco’s modified Eagle’s minimal essential medium ELISA, enzyme-linked immunosorbent assay fMLP, N-formyl-methionyl-leucyl-phenylalanine IL, interleukin LPS, lipopolysaccharide PBS, phosphate-buffered saline.