Summary

Neutrophil functions were examined in healthy periparturient dairy cows (n = 46) and in cows with retained placenta and metritis complex (n = 20); metritis (n = 18); or mastitis (n = 13). Blood samples (50 ml) were collected from each cow via jugular vein twice weekly from 1.5 weeks before to 4 weeks after parturition. Neutrophil function was evaluated, using 6 tests: random migration, chemotaxis, ingestion, myeloperoxidase activity (iodination), superoxide production (cytochrome C reduction), and antibodydependent cell-mediated cytotoxicity. Ability to ingest bacteria and random migration activity of neutrophils from clinically normal cows were high around parturition and increased immeidately after parturition, whereas myeloperoxidase activity and antibody-dependent cell-mediated cytotoxicity ability of neutrophils from these cows decreased after parturition. Measurement of neutrophil function in 4 over-iectomized cows revealed significant (P < 0.0005) seasonal changes in results of all 6 functional assays. We observed various defects of neutrophil function in all cows with abnormal conditions after parturition. Before parturition, superoxide production activity by neutrophils from cows with metritis and chemotaxis by neutrophils from cows with mastitis were significantly (P < 0.001 and P < 0.05, respectively) lower, indicating that a defect of neutrophil function may be a predisposing factor in the development of these disorders. In conclusion, the host defense role of neutrophils in periparturient cows was impaired, principally because of a defect in killing capacity, which may increase susceptibility to infections. We also investigated the in vitro effects of arachidonic acid metabolites and recombinant human colonystimulating factors (rhcsf) on functions of neutrophils from clinically normal and postparturient cows with abnormalities, including retained placenta, metritis, or mastitis (n = 5/group). Each abnormal cow was matched for postpartum period with a clinically normal cow. Neutrophils from individual cows were preincubated with arachidonic acid metabolites (prostaglandin F_2a, 10⁻⁷M; prostaglandin E_2, 10⁻⁶M; leukotriene B₄, 10⁻⁸M; and lipoxin B, 10⁻⁸M) and rhcsf (rh-granulocyte-csf, 1,000 or 6,000 U/ml; rh-granulocyte-macrophage-csf, 5 or 15 ng/ml) in a 37 C water bath for 30 minutes before submitting them to function assays. There was no response by neutrophils from either clinically normal or abnormal postparturient cows to treatment with either arachidonic acid metabolites or rhcsf in any of the 6 functional assays. However, preincubation of neutrophils alone in a 37 C water bath for 30 minutes resulted in some alteration of neutrophil function. This may indicate translocation of receptors between an intracellular pool and the cell surface, as well as differences in receptor numbers or signal transduction mechanisms in these abnormal cows.