Effect of acute-phase proteinase inhibitors on chemotaxis of rat polymorphonuclear leukocytes in vitro.

Rat serum obtained at 24 h after subcutaneous injection of carrageenin significantly suppressed chemotaxis of rat polymorphonuclear leukocytes (PMNs) in vitro. alpha 2 Acute-phase macroglobulin (alpha 2APM), alpha 1 proteinase inhibitor (alpha 1 PI) and cysteine-proteinase inhibitors (CPIs) are present at high concentration in the 24-h serum and known as acute-phase reactants in rats. These acute-phase proteinase inhibitors were purified from inflamed rat serum or exudate and their effect on PMN chemotaxis was studied by Boyden's method in vitro. alpha 2 APM (4 mg/ml) significantly suppressed PMN chemotaxis while alpha 1M was without effect, though both alpha 2APM and alpha 1M had a similar anti-proteinase activity. The results suggest that alpha 2APM suppressed PMN chemotaxis through the mechanism unrelated to its anti-proteinase activity. On the other hand, alpha 1PI (1 and 3 mg/ml) slightly but significantly suppressed PMN chemotaxis, whereas CPI-1 and CPI-2 had no inhibitory effect. These results suggest that alpha 2APM and alpha 1PI play a role in suppression of PMNs infiltration into the inflammatory site in the late-phase of acute inflammation.