The isolation, long-term cultivation and characterization of bovine peripheral blood monocytes.

Bovine peripheral blood monocytes were isolated from buffy coats of ACD-anticoagulated whole blood. Cells cultivated on plastic surfaces for 20 h were judged to be 95% monocytes based on nonspecific esterase-1 staining, uptake of latex particles and surface receptor characteristics. Bovine monocytes were maintained up to 80 days in vitro in Dulbecco's modified Eagle medium with 15% horse serum and 15% foetal bovine serum. Several morphological and physiological features of bovine monocytes were examined during the course of culture. Cell size and cytoplasmic spreading, granulation and vacuolization increased progressively. Multinucleated giant cells predominated during the latter stages of in vitro culture. A high percentage of bovine monocytes possessed C3 and IgG Fc receptors, whereas IgM Fc and sheep erythrocyte receptors were not detected. Phagocytosis was mediated by the IgG receptor, but not by the C3 receptor. Peroxidase activity declined in a linear fashion, with cells essentially negative after 8 days of culture. Total cell protein and acid phosphatase increased during cultivation. Lysozyme activity was undetectable in both lysates and supernatants of bovine monocyte. These findings are consistent with the concept of maturation of mononuclear phagocytes. The procedures for isolation and cultivation described in this paper will provide methodology for detailed study of bovine mononuclear phagocytes.