Interaction between the respiratory burst activity of neutrophil leukocytes and experimentally induced Escherichia coli mastitis in cows

The respiratory burst activity of neutrophil leukocytes from bovine peripheral blood was studied before and during an experimentally induced Escherichia coli mastitis. The competence of neutrophils to generate reactive oxygen species following stimulation with opsonized particles prior to infection was negatively correlated with severity of subsequently induced E. coli mastitis. In the presence of the soluble activator, phorbol myristate acetate, no such correlation was obtained. However, combination of blood neutrophil numbers with phorbol myristate acetate induced respiratory burst competence, called reactive oxygen species-generating capacity, displayed a negative correlation with the intensity of a subsequent inflammation of the bovine mammary gland. At the onset of mastitis, a concomitant reduction in blood neutrophil numbers, a strong shift in cell types, and a substantial decrease in production of reactive oxygen species occurred. Reestablishment and even enhancement of the respiratory burst activity coincided with the reappearance of mature neutrophils. Possible stimulatory effects on neutrophil superoxide generation are discussed. Data suggest that generation of reactive oxygen species by mature neutrophils may be of primary importance for microbial killing during the onset and recovery from mastitis.