Cytokine kinetics were examined in milk and in afferent and efferent lymph of the supramammary lymph node after intramammary infusion of endotoxin from Escherichia coli. Cows were sampled 0, 2 and 4 h after infusion (p.i.). Neutrophils appeared in afferent lymph 2 h p.i., and in efferent lymph and milk 4 h p.i. The milk contained high concentrations of interleukin-8 (IL-8) at 2 and 4 h p.i. IL-8 was also found in lymph, but at lower concentrations. The tumor necrosis factor-α (TNF-α) concentration tended to increase in afferent lymph at 2 h p.i., and increased in milk at 4 h p.i. The level of IL-1β increased at 4 h p.i. in milk, but was not detected in lymph. Interferon-γ was not detected in any sample, at any time. The results indicate a primary role for IL-8 in the recruitment of neutrophils into the gland, and suggest that IL-1β and TNF-α are not necessary for IL-8 production and release in response to endotoxin.
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