Cytokines in mammary lymph and milk during endotoxin-induced bovine mastitis

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.