Sequential study of pleural peritoneal and blood cells in acute pleurisy induced by calcium pyrophosphate in the rat.

We studied the sequential cellular events that occur during nonspecific pleurisy induced by a nondiffusible, nonantigenic and endotoxin-free irritant, calcium pyrophosphate (CaPP). The study was conducted over 10 days and concerned not only the pleural cavity but also the peritoneal cavity and the blood. After injection of CaPP, the first cellular event in the pleural space was a "leukocyte disappearance reaction," followed by an important increase in the polymorphonuclear leukocytes (PMN) and then by an increase in the macrophages. This phase is also characterized by the appearance of submesothelial nodules composed of macrophages and numerous polymorphonuclear cells. All the cell populations returned to their normal value on day 10, although granulomatous submesothelial nodules were present. In the blood, the principal observation was an increased PMN count associated with a decreased lymphocyte count at 4 h. In the peritoneal cavity, it was remarkable that, although functional modifications have been reported in the same model, the different leukocyte populations did not vary during the reaction.