In contrast to acute inflammation caused by Escherichia coli (E. coli) infection of the mammary gland, S. aureus causes a delayed inflammatory response in cows, mainly in the form of low concentrations of neutrophil chemo-attractants [interleukin (IL)-8, complement component 5a (C5a)] and neutrophil potent activators [tumor necrosis factor (TNF)-α] in milk (3). Here, TNF is linked to escherichia coli infection.