Examination of chemotactic properties of bovine mammary macrophages

An in vitro model system in which polymorphonuclear leukocytes (PMN) migration under agarose was employed to examine the ability of mammary macrophages to release chemoattractants for PMN. Mammary macrophages were incubated in Hanks' balanced salt solution for up to 12 h in the presence of Staphylococcus aureus. The possibility that the chemotactic activity is mediated through release of interleukin 1 (IL-1) and prostaglandins (PGs) by mammary macrophages was investigated. The data showed that release of chemotactic activity peaked 6 h following addition of S. aureus in the culture medium of mammary macrophages. Very low levels of IL-1 were detected in the same culture medium. Addition of indomethacin, a PGs synthesis inhibitor, was ineffective in altering the chemotactic activity detected in the culture medium of macrophages. These data suggest that it is highly unlikely that the chemotactic activity is mediated through the production of IL-1 and PGs by the mammary macrophages.