Effect of type A Pasteurella multocida fractions on bovine polymorphonuclear leukocyte functions

Abstract

The effect of various Pasteurella multocida fractions on bovine polymorphonuclear leukocyte (PMN) functions was examined in vitro by using two encapsulated strains, P-2383 and P-1062 (both are Carter capsular type A and of bovine origin). The ability of PMNs to ingest Staphylococcus aureus and iodinate protein was significantly inhibited in the presence of live cells, heat-killed whole cells, or saline-extracted capsules but not in the presence of the decapsulated heat-killed cells. None of the fractions of the two strains inhibited nitroblue tetrazolium reduction by PMNs. The saline extract did not inhibit the binding of iodine to protein by a reaction involving xanthine, xanthine oxidase, and horseradish peroxidase. The PMN inhibitory factor was further characterized as a heat-stable capsular material of greater than 300,000 molecular weight.