Cytokine response of bovine mammary gland epithelial cells to Escherichia coli, coliform culture filtrate, or lipopolysaccharide

Abstract

Objective - To define the cytokine response of a cultured mammary gland epithelial cell line (ie, Mac-T) when incubated with Escherichia coli or its products. Sample population - Mac-T cells and E coli from cows with mastitis. Procedure - Mac-T cells were incubated with E coli or its products. The cytokine response of Mac-T cells to these treatments was quantified by measuring mRNA content of interleukin (IL)-1α, IL-1β, IL-8, and tumor necrosis factor (TNF)-α by use of a quantitative reverse transcriptase-polymerase chain reaction assay. The amount of TNFα secreted was also measured. Results - Treatment with E coli or its products resulted in significant increases in IL-1α, IL-8, and TNFα mRNA content in Mac-T cells. This increase was reversible when culture filtrate was incubated with polymyxin B. The amount of IL-1β mRNA in Mac-T cells increased only slightly over baseline after treatment with E coli or its products, but this increase was not diminished by incubation of E coli filtrate with polymyxin B. Conclusions and clinical relevance - Incubation of Mac-T cells with E coli or its products resulted in increased amounts of IL-1α, IL-8, and TNF-α mRNA. Inhibition of this response by incubation of culture filtrate with polymyxin B suggested that lipopolysaccharide was the main bacterial product that stimulated the cytokine response. The small increase in IL-1β content in Mac-T cells incubated with E coli or its products suggested that this cytokine had a smaller role in the Mac-T cell response to E coli.