Determination of cytokine (+) cells in the small intestine tissues. Positive cells were counted in histological sections from small intestine of mice fed 7 d with L. casei CRL 431 previous challenge with S. Typhimurium (Lc-S), and mice fed continuously (before and after infection) with the probiotic bacteria (Lc-S-Lc), compared to the infection control (S). Tissues from healthy mice fed or not with L. casei (Lc and C groups, respectively) were also analyzed. The samples were obtained the day of the infection (basal data) for Lc and C groups, and 7 and 10 days post challenge for all the groups. Representative microphotographs show the differences observed between C group (E and F), S group (G and H), and Lc-S-Lc group (I and J) in the number of IL-6 (+) cells (arrows), 7 days post challenge. The microphotographs E, G and I were obtained at 400× while F, H and J were taken at 1 000X. A difference of 1 cell at 1000× is related with 10 cells of difference in the final result. Means for each value without a common letter differ significantly (P < 0.01).