Comparative studies on inflammatory reactions induced by non-immunological and immunological stimuli in an air pouch and in a carboxymethyl cellulose (CMC)-induced inflammatory pouch.

Inflammatory reactions were compared in the air pouch and the CMC pouch. Inflammation was induced by injection of CMC as a non-specific irritant, lipopolysaccharide (LPS) as an activator of macrophages, and methylated bovine serum albumin (m-BSA) as an inducer of delayed type hypersensitivity. There was no prominent difference in the inflammatory reactions following injection of 2% CMC solution into a 4-day-old air pouch and a 3-day-old CMC pouch. On the other hand, injection of 4 ml of 100 ng/ml LPS into each of the pouches enhanced the inflammatory reactions in the CMC pouch several-fold compared with those in the air pouch. A similar tendency was found in the case of an injection of 1 ml of 1 mg/ml m-BSA in rats sensitized with 1 mg of m-BSA. The enhanced inflammatory reactions induced by the injection of LPS or m-BSA were inhibited by dexamethasone, but not by indomethacin. These results indicate that the enhanced inflammatory reactions induced by CMC are related to lining tissue formation, which was a common characteristic in both pouches. Enhanced inflammatory reactions following injection of LPS and m-BSA were related to the activation of macrophages and newly formed blood vessels, which were not characteristic features in the air pouch, but were in the CMC pouch, in addition to the lining tissue. Cyclo-oxygenase products were not associated with the reactions.