['Because tolerance to food is potentially modulated by IL-10, strategies to prevent food allergy should favor an increased delivery of IL-10 to the gut.', 'We hypothesized that administration of a Lactococcus lactis transfected to secrete murine IL-10 could prevent sensitization in a mouse model of food allergy.', 'Before each oral sensitization with beta-lactoglobulin in the presence of cholera toxin, young mice were administered the transfected Lactococcus lactis. Antigen-induced anaphylaxis after oral challenge assessed clinical protection achieved by the pretreatment. Serum and feces antigen-specific antibody concentrations were sequentially measured. Antibody titers were correlated with antibody and IL-10-secreting cell numbers in the spleen and in Peyer patches.', 'Pretreatment with transfected Lactococcus lactis contributed to diminish anaphylaxis significantly, and inhibit antigen-specific serum IgE and IgG(1) production strongly. In addition, transfected Lactococcus lactis increased the production of antigen-specific IgA in the gut. Variations of antibody levels in the serum and the gut correlated with the numbers of antibody-producing cells. In addition, the presence of exogenous IL-10 in the gut by transfected Lactococcus lactis induced IL-10 secretion by Peyer patches cells. Increased IL-10 titers were also measured in the plasma.'] Does oral administration of an IL-10-secreting Lactococcus lactis strain prevent food-induced IgE sensitization?