Evidence for the activation of blood complement in Sephadex beads-induced lung inflammation in guinea pigs

Objective and Design: This study evaluated the complement activation in guinea pigs that were given an intravenous injection of Sephadex and its correlation with markers of the development of inflammation. Materials and Methods: Dunkin Hartley guinea pigs (250-300 g) were used. Whole blood was collected by heart puncture in a sodium citrate solution (0.315 g/ml) for complement measurements. Complement activation was measured using a colorimetric haemolytic assay. Bronchoalveolar lavages (BAL) were performed to monitor cell infiltration and inflammation was monitored by measurements of eosinophil peroxidase (EPO), histamine, beta-glucuronidase, albumin and total proteins in the BAL fluid. Treatment: Guinea pigs were pre-treated with aprotinin (40 000 IKU/kg) 30 min before they were given an intravenous injection of Sephadex beads (24 mg/kg). Carboxymethyl (CM)-Sephadex (24 mg/kg) was administered alone. Results: Sephadex beads activated the complement system in vitro (14.12 +/- 2.29 U/ml) and in vivo (9.95 +/- 0.08 U/ml) reaching a peak 6 h after the injection. This activation was accompanied by other characteristic features of inflammation such as leukocyte infiltration and activation. Both CM-Sephadex and aprotinin reduced the blood complement activation and eosinophil infiltration/activation observed. Conclusions: Our results strongly suggest that complement is involved in the cascade of events leading to the inflammatory state observed in guinea pig following the intravenous injection of Sephadex beads.