The inflammatory response to paraffin in the peritoneal cavity of the rat

The inflammatory response to intraperitoneal paraffin in hte rat has been defined in terms of the fluid influx and the pattern of cell accumulation. The volume of fluid exudate in the peritoneal cavity was small and did not change dramatically with time, but there was a moderate cellular influx which was biphasic with peaks at 24 and 72 h. Mononuclear phagocytes and eosinophils were the major cell types found in the exudate, neutrophils, lymphocytes, and mast cells being much less numerous. The neutrophil influx was apparent by 4 h. It was early, short-lived and of low magnitude. In contrast, the eosinophil response was later and more prolonged, cell numbers reaching a peak at 72 h when they were the predominant cell type. The response of the mononuclear phagocytes was multiphasic, with peaks in cell numbers occurring at 24 and 96 h, and 3 weeks after stimulation, by which time they exhibited the morphological features of large activated macrophages which were highly phagocytic for paraffin. The method is useful for the production of mixed inflammatory cell populations from which the fluid phase can readily be separated, and may be a valuable model for the study of esoinophil kinetics.