Blockade by antimacrophage serum of the migration of PMN neutrophils into the inflamed peritoneal cavity.

The effect of rat antimacrophage serum (rAMS) was tested on the influence of normal or thioglycollate-stimulated macrophage populations of the rat peritoneal cavity on the migration of polymorphonuclear neutrophils (PMN) induced by carrageenin, heterologous serum (rabbit) and sheep red blood cells. The rAMS used did not cross-react with PMN or lymphocytes nor did it affect circulating white cells, complement levels or lysed PMN present in the inflammatory exudate. It did, however, give a positive immunofluorescence reaction with resident and stimulated macrophages. The rAMS inhibited macrophage function as tested by sheep red blood cell phagocytosis in vivo and release of a PMN chemotactic factor(s) in vitro. Thioglycollate-stimulated peritoneal cavities showed an increased macrophage population and responded with increased PMN migration when challenged with heterologous serum or carrageenin, as compared with control rats. The presence of rat antimacrophage antibodies inhibited PMN migration induced by heterologous serum, sheep red blood cells and carrageenin. It is concluded that resident macrophages participate in the control of PMN migration to the site of an acute inflammation by acting as 'alarm cells' and triggering several defence mechanisms which ultimately protect the host from injurious stimuli.