Recombinant Bovine Interleukin-1β Amplifies the Effects of Partially Purified Pasteurella haemolytica Leukotoxin on Bovine Neutrophils in a β(2)-Integrin-Dependent Manner

The influx and death of polymorphonuclear leukocytes within the infected lung are hallmarks of bovine pasteurellosis. Recent reports have shown that the Pasteurella haemolytica leukotoxin (LKT) and other RTX toxins bind β(2)-integrins on target cells. In this study we demonstrate that exposure of bovine neutrophils to recombinant bovine interleukin-1β upregulates β(2)-integrins (CD11a/CD18), which in turn enhance the binding and amplify the biological effects of partially purified LKT on these cells. LKT binding and cytotoxicity were inhibited by addition of an anti-integrin antibody (CD11a/CD18). These findings help to clarify the early events that occur in bovine pasteurellosis and support the hypothesis that inflammatory mediators might increase the severity of pasteurellosis by causing upregulation of β(2)-integrins that serve as an LKT receptor on bovine neutrophils.