ASSOCIATION BETWEEN NEUTROPHIL FUNCTIONS AND PERIPARTURIENT DISORDERSIN COWS

Neutrophil functions were examined in healthy periparturient dairy cow s (n = 46) and in cows with retained placenta and metritis complex (n = 20); metritis (n = 18); or mastitis (n = 13). Blood samples (50 mi) were collected from each cow via jugular vein twice weekly from 1.5 we eks before to 4 weeks after parturition. Neutrophil function was evalu ated, using 6 tests: random migration, chemotaxis, ingestion, myeloper oxidase activity (iodination), superoxide production (cytochrome C red uction), and antibody-dependent cell-mediated cytotoxicity. Ability to ingest bacteria and random migration activity of neutrophils from cli nically normal cows were high around parturition and increased immedia tely 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 overiectomized cows revealed significant (P < 0.0005) seasonal ch anges in results of all 6 functional assays. We observed various defec ts of neutrophil function in all cows with abnormal conditions after p arturition. Before parturition, superoxide production activity by neut rophils from cows with metritis and chemotaxis by neutrophils from cow s with mastitis were significantly (P < 0.001 and P < 0.05, respective ly) lower, indicating that a defect of neutrophil function may be a pr edisposing factor in the development of these disorders. In conclusion , the host defense role of neutrophils in periparturient cows was impa ired! principally because of a defect in killing capacity, which may i ncrease susceptibility to infections. We also investigated the in vitr o effects of arachidonic acid metabolites and recombinant human colony -stimulating factors (rhCSF) on functions of neutrophils from clinical ly normal and postparturient cows with abnormalities, including retain ed placenta, metritis, or mastitis (n = 5/group). Each abnormal cow wa s matched for postpartum period with a clinically normal cow. Neutroph ils from individual cows were preincubated with arachidonic acid metab olites (prostaglandin F-2 10(-7)M; prostaglandin E(2), 10(-6)M; leukot riene B-4, 10(-8)M; and lipoxin B, 10(-8)M) 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 functi on assays. There was no response by neutrophils from either clinically normal or abnormal postparturient cows to treatment with either arach idonic acid metabolites or rhCSF in any of the 6 functional assays. Ho wever, preincubation of neutrophils alone in a 37 C water bath for 30 minutes resulted in some alteration of neukophil function. This may in dicate translocation of receptors between an intracellular pool and th e cell surface, as well as differences in receptor numbers or signal t ransduction mechanisms in these abnormal cows.