Kayoko Kimura

Activation of Immune Cells in Bovine Mammary Gland Secretions by Zymosan-Treated Bovine Serum

Mastitis, caused by bacterial infection of the mammary gland, is a major disease of dairy cattle. The greatest risks of intramammary infection occur at the end of lactation and at the initiation of the next lactation when the cow calves. Treating serum with zymosan (yeast cell wall preparation) causes the complement to cleave, allowing this serum to serve as a source of complement fragment 5a (C5a), a potent chemoattractant and activator of the immune system. Our hypothesis was that intramammary infusion of zymosan-treated serum (ZTS) would recruit polymorphonuclear neutrophils (PMN) and generate prolonged activity in lymphocytes within the mammary gland. Ultimately this could help prevent bacterial infections in cows at dry-off and at the initiation of lactation. Two ipsilateral quarters of the mammary gland of each cow were infused with ZTS (12.5 mL/quarter), and 2 contralateral quarters were infused with saline in 8 cows shortly after lactation ended. Mammary secretions were collected periodically throughout the dry period and the first 2 wk of the next lactation. Activation status of lymphocytes and PMN in those secretions was assessed based on the intracellular presence or absence of IFN-gamma and IL-8 as determined by flow cytometry. The ZTS infusion greatly increased PMN numbers in mammary secretions for the first week only. The percentage of IFN-gamma positive lymphocytes and PMN, and the percentage of IL-8 positive PMN, exhibited a sustained increase in secretions from ZTS-treated quarters through the first 2 wk of lactation. The ZTS can stimulate PMN and lymphocyte-mediated immune defense mechanisms in the mammary gland, which may provide a useful means of preventing new intramammary infections during the dry period as well as at the initiation of lactation.

Association Between Retained Placenta and Impaired Neutrophil Function in Dairy Cows

Materials and Methods The ability of the neutrophils to recognize fetal tissue was assessed by a chemotaxis assay (CHEM). In this assay fetal placenta homogenate from a normally expelled placenta is placed in the bottom of a Boyden chamber. A porous polycarbonate membrane is placed over the homogenate and whole blood is placed in the top portion of the chamber. The polycarbonate membrane allows placental chemoattractants to pass into the upper chamber and attract neutrophils to bind to the membrane. After 30 min incubation the number of neutrophils attached to the polycarbonate membrane were counted under the microscope. Typically in cows that responded well to the placental chemoattractants around 400 neutrophils were counted in 5 microscope fields. Neutrophil killing abilities were estimated by determining myeloperoxidase activity in a protein iodination assay (IOD) and these results are expressed as a % of lab. controls. Blood samples were obtained periodically prior to calving and for the first day after calving from 39 cows (7 cows developed RP) on one farm and 103 cows (13 cows developed RP) at another.