| The purpose of this study was to test the hypothesis that probiotics could enhance immune function by stimulating cytokine secretion by intestinal epithelial cells. To test this hypothesis, the effects of fermented and non-fermented reconstituted non-fat dry milk containing probiotic cultures (Lactobacillus acidophilus, L. bulgaricus, L. casei, L. reuteri, Streptococcus thermophilus, Bifidobacterium, B. adolescentis) on interleukin (IL)-6 and IL-8 production by Caco-2 cells were assessed. Three different concentrations (106, 107, 108 CFU/ml) of probiotic cultures were used to determine the optimum dose to elicit a maximal immune response. Probiotic cultures were inactivated by heat (95°C, 30 min) or irradiation (1 Mrad). In addition, milk components (lactose, alpha-lactalbumin, beta-lactoglobulin) were evaluated for their ability to stimulate IL-6 and IL-8 production. In general, none of the cultures investigated significantly stimulated IL-6 or IL-8 production. There was a significant difference, however, between heat- and irradiation-inactivated samples. Heat-inactivated cultures caused more IL-6 and IL-8 production than their irradiated counterparts. These results suggest that the mode of inactivation may be important to immune stimulation. The milk components, alpha-lactalbumin and beta-lactoglobulin elicited markedly high amounts of IL-6 and IL-8 production from Caco-2 cells. These results suggest that certain milk components have immunostimulating abilities in the gastrointestinal tract. |
