| actic acid bacteria are essential for the fermentation of products such as cheese, buttermilk and yogurt. An increasing number of functional foods and pharmaceutical preparations are being promoted with health claims based on the potential probiotic characteristics of some of these bacteria and on their capacity for stimulating the host immune system. A possible mechanism for these effects is direct stimulation of the gastrointestinal immune response. The specific objectives of these studies were to evaluate the effects of in vivo, ex vivo, and in vitro exposure to viable, non-viable strains, and cell extracts of lactic acid bacteria (Lactobacillus acidophilus, L. bulgaricus, L. casei, L. gasseri, L. helveticus, L. reuteri, Streptococcus thermophilus and Bifidobacterium) on leukocyte function. In vivo studies showed that growth rate of mice as well as immunoglobulin levels were not affected by direct oral administration of lactic acid bacteria. Although basal cytokine mRNA expression in spleen and Peyer's patches was not affected by repeated oral lactic acid bacteria administration (in vivo), single exposures to certain bacteria altered subsequent mitogen induced cytokine and nitric oxide production by peritoneal cells (ex vivo). When mice were fed a fermented milk manufactured with starter cultures containing different species/strains of lactic acid bacteria for three weeks and after immunizing twice with 10... |
