Gene expression of immunologically important factors in blood cells, milk cells, and mammary tissue of cows.

Cytokines, eicosanoids, and lactoferrin are involved in the mammary gland's immune response to invading microorganisms. The goal of this work was to investigate the synthesis of these immunologically important factors in somatic milk cells, blood cells, and mammary tissue of cows with different somatic cell count levels, i.e., different immunological activity. On the level of mRNA expression, the cytokine tumor necrosis factor alpha (TNFalpha), lactoferrin (Lf), and specific key enzymes of leukotriene and prostaglandin biosynthesis, 5-lipoxygenase (5-LO), and cyclooxygenase-1 (COX-1) and -2 (COX-2), respectively, were determined. All 15 experimental cows were clinically healthy with no visible mammary disease. Eight cows were defined as control group with all quarters <150,000 cells/ml (C), whereas seven cows had partially elevated quarter somatic cell counts, with at least one quarter >150,000 cells/ml (H) and one quarter <150,000 cells/ml (L). Total quarter milk from one quarter of control group and from two quarters of cows with partially elevated cell counts (one of H and one of L) was collected at one milking and a blood sample was taken simultaneously. In addition, mammary tissue samples were taken from the respective quarters on the following day during slaughter. Total RNA from milk, blood, and tissue cells was isolated and reverse transcription and quantitative polymerase chain reaction was carried out. All factors investigated were not significantly different between groups in blood cells and between C and L quarters in milk cells and mammary tissue. TNFalpha and COX-2 mRNA expression was higher in milk cells and mammary tissue of H than in L quarters, except for COX-2 in mammary tissue. Generally, TNFalpha and COX-2 showed their highest expression in milk cells, 5-LO in blood cells, whereas lactoferrin was mainly expressed by the mammary tissue. COX-1 was similarly expressed in all tested samples.