Experimental mastitis. Milk samples were analysed at different times for intramammary bacterial infection (pannel A; CFU, left y-axis), inflammatory mediator (pannel A; TNF-α; right y-axis), and for somatic cell profil (pannel B). Data are expressed as mean ± standard error of the mean. During the first 6 hours post-challenge, mean values of 4 cows are reported. By 6 hours, two cows were not sampled because they received antibiotics (Materials and Methods). Error bars, standard error of the means.