Changes in blastogenic activity of bovine blood mononuclear cells throughout the nonlactating period

Mononuclear cells were isolated from bovine blood by density gradient centrifugation to determine variation in mitogen-induced mononuclear cell activity throughout the nonlactating period. In a preliminary study, optimum concentrations of Concanavalin A, phytohemagglutinin, Salmonella typhimurium lipopolysaccharide, and three Escherichia coli lipopolysaccharides were determined using six cows as blood donors. Concanavalin A, phytohemagglutinin, and E. coli 0111:B4 lipopolysaccharide were selected for further studies. Mitogenic responses of blood mononuclear cells from five cows were evaluated at drying off, 14 to 16 and 28 to 30 d of involution, 12 to 14 d prepartum, and at parturition. Concanavalin A-treated cells exhibited greater blastogenic activity than phytohemagglutinin-treated cells. Response of cells to Concanavalin A increased slightly through 28 to 30 d of involution and decreased markedly at parturition. Blastogenic activity of cells treated with phytohemagglutinin decreased throughout the nonlactating period and was lowest at parturition. Activity of lipopolysaccharide-treated mononuclear cells increased through 28 to 30 d of involution. However, response of mononuclear cells to lipopolysaccharide was minimal compared with response to Concanavalin A and phytohemagglutinin. Variation in peripheral blood mononuclear cell activity throughout involution may parallel mammary gland mononuclear cell activity, affecting susceptibility of the mammary gland to new intramammary infections.