A comparative study of the cellular, exudative and histological responses to carrageenan, dextran and zymosan in the...

A murine 6-day air-pouch model of inflammation has been developed and used to compare the patterns of acute and chronic inflammatory response to three irritants, carrageenan, dextran and zymosan, each injected into the cavity of the pre-formed pouch. The inflammation was assessed by measurement of exudate volume and numbers of infiltrating leucocytes over a 30-day time course. Histological changes in the inflamed air-pouch lining tissue were also investigated. The inflammatory response to carrageenan was acute with moderate exudate formation and cell numbers. Dextran produced a mild inflammatory reaction with low cell infiltration into exudate. In contrast, the inflammatory response to zymosan was greater in terms of cell migration, but smaller in terms of exudate volume and occurred later in the time course. Histological changes in the inflamed air-pouch tissue were also markedly different in response to the three irritants. Carrageenan induced a rapid, mainly polymorphonuclear leucocyte (PMN) infiltrate into the tissue and deposition of fibrin on the luminal surface. The response to dextran was characterized by a rapid resolution of the inflammatory response, with fewer leucocytes present in the lining and no fibrin deposition. In contrast, zymosan caused a marked but slower leucocyte influx, with greater numbers of monocytes, and clearance of the zymosan particles from the air-pouch lining by macrophages. This study indicates that by using different irritants to produce inflammation, it may be possible to dissect the roles played by various cells and inflammatory mediators during acute and chronic inflammation.