Acute induction of interleukin-6 and biphasic changes of serum complement C3 by carrageenan in mice.

Carrageenan has been widely used as an irritant to evoke inflammation in animals or to selectively deplete macrophages in vivo. Although precise understanding of carrageenan activity is a prerequisite for the experimental use of this polysaccharide, the effects of this agent on host-biological systems are still poorly understood. We investigated the effect of carrageenan on serum concentrations of complement C3 and interleukin (IL)-6, a potent complement-inducing factor. Intraperitoneal administration of carrageenan (4 mg) in mice resulted in an initial fall in serum C3 (70% of control, P < 0.05) between 3 and 6 h, but was followed by a significant rise (180% of the control, P < 0.05) at 24h. Prior to the rise in complement C3, a sharp peak of serum IL-6 was observed at 6h after carrageenan treatment. These results indicate potential of carrageenan to enhance host complement systems, which may be associated with, at least in part, an acute induction of IL-6.