Polymorphonuclear leukocytes and the induction of alpha 2-macroglobulin synthesis

Peritoneal exudate-polymorphonuclear leukocytes (PMNLs) secreted a factor, PMN factor (PMN-F), which stimulated hepatocytes to synthesize alpha 2-macroglobulin (a2M), in vitro. The synthesis of a2M was enhanced by the factor in the presence of dexamethasone (Dex), and the effect was dose-dependent. After harvesting from the peritoneal exudate, PMNLs released the factor within 1 hr of the incubation. Physicochemical properties of the factor were as follows: nondialyzable, heat-labile, stable in wide pH change, inactivated by a protease inhibitor, aprotinin, and apparent molecular weight being 12,000-21,000, determined by gel filtration. Treatment of PMNLs with zymosan resulted in increases in the activity of lysosomal enzymes but not that of the factor. These results indicate that the factor is a protease other than lysosomal enzymes.