Lactobacilli and bifidobacteria induce differential interferon-ß profiles in dendritic cells.

The health promoting effects of probiotics are well-documented; however, current knowledge on immunostimulatory effects is based on data from a single strain or a limited selection of strains or species. Here, we compared the capacity of 27 lactobacilli and 16 bifidobacteria strains to stimulate bone marrow-derived dendritic cells (DC). Most lactobacilli strains, including Lactobacillus acidophilus, Lactobacillus gasseri, Lactobacillus casei and Lactobacillus plantarum, induced strong IL-12 and TNF-α production and up-regulation of maturation markers. In contrast, all bifidobacteria and certain lactobacilli strains were low IL-12 and TNF-α inducers. IL-10 and IL-6 levels showed less variation and no correlation with IL-12 and TNF-α. DC matured by strong IL-12-inducing strains also produced high levels of interferon (IFN)-ß. When combining two strains, low IL-12 inducers inhibited this IFN-ß production as well as IL-12 and Th1-skewing chemokines. The IFN-ß induction was mediated through c-Jun N-terminal kinase (JNK) irrespective of the stimulating strain. The inhibitory bacteria induced higher levels of the transcription factor c-Jun dimerization protein (JDP)-2, thereby counteracting the effect of JNK. Our data demonstrate that lactobacilli can be divided into two groups of bacteria featuring contrasting effects, while all bifidobacteria exhibit uniform effects. This underlines the importance of selecting the proper strain(s) for probiotic purposes.

Immunomodulating potential of supplementation with probiotics: a dose-response study in healthy young adults.

Certain probiotic microorganisms have been found beneficial in the treatment of immune-related diseases and may also affect immune function in healthy people. Intervention studies of probiotics in healthy humans are urgently required. Here, the immunomodulating potential of Bifidobacterium animalis ssp. lactis (BB-12) and Lactobacillus paracasei ssp. paracasei (CRL-431) was studied in a double-blind placebo-controlled parallel dose-response trial (n=71) based on five randomly assigned groups of young healthy adults supplemented for 3 weeks with 0, 10(8), 10(9), 10(10) and 10(11) CFU day(-1), respectively, of a mixture of BB-12 and CRL-431. No statistically significant dose-dependent effect was found for phagocytic activity in blood leukocytes, fecal immunoglobulin A (IgA) concentrations or production of interferon-gamma and interleukin-10 in blood cells. When evaluating data according to the amount of viable BB-12 recovered from faeces, the interferon-gamma production in blood cells was significantly reduced. In conclusion, no solid effect on the immune function of young healthy adults supplemented with even high doses of B. animalis ssp. lactis BB-12 and L. paracasei ssp. paracasei CRL-431 was demonstrated in this study.

Lactic acid bacteria inducing a weak interleukin-12 and tumor necrosis factor alpha response in human dendritic cells inhibit strongly stimulating lactic acid bacteria but act synergistically with gram-negative bacteria.

The development and maintenance of immune homeostasis indispensably depend on signals from the gut flora. Lactic acid bacteria (LAB), which are gram-positive (G+) organisms, are plausible significant players and have received much attention. Gram-negative (G-) commensals, such as members of the family Enterobacteriaceae, may, however, be immunomodulators that are as important as G+ organisms but tend to be overlooked. Dendritic cells (DCs) are crucial immune regulators, and therefore, the present study aimed at investigating differences among human gut flora-derived LAB and G- bacteria in their patterns of DC polarization. Human monocyte-derived DCs were exposed to UV-killed bacteria, and cytokine secretion and surface marker expression were analyzed. Profound differences in the DC polarization patterns were found among the strains. While strains of LAB varied greatly in their capacity to induce interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-alpha), G- strains were consistently weak IL-12 and TNF-alpha inducers. All strains induced significant amounts of IL-10, but G- bacteria were far more potent IL-10 inducers than LAB. Interestingly, we found that when weakly IL-12- and TNF-alpha-inducing LAB and strong IL-12- and TNF-alpha-inducing LAB were mixed, the weakly IL-12- and TNF-alpha-inducing LAB efficiently inhibited otherwise strong IL-12- and TNF-alpha-inducing LAB, yet when weakly IL-12- and TNF-alpha-inducing LAB were mixed with G- bacteria, they synergistically induced IL-12 and TNF-alpha. Furthermore, strong IL-12- and TNF-alpha-inducing LAB efficiently up-regulated surface markers (CD40, CD83, CD86, and HLA-DR), which were inhibited by weakly IL-12- and TNF-alpha-inducing LAB. All G- bacteria potently up-regulated surface markers; however, these markers were not inhibited by weakly IL-12- and TNF-alpha-inducing LAB. These much divergent DC stimulation patterns among intestinal bacteria, which encompass both antagonistic and synergistic relationships, support the growing evidence that the composition of the gut flora affects immune regulation and that compositional imbalances may be involved in disease etiology.

Effect of maternal dietary cow's milk on the immune response to beta-lactoglobulin in the offspring: a four-generation study in mice.

BACKGROUND: Evaluation of immune responses to food proteins in animal models requires that the animals are not already sensitized or orally tolerized against the proteins in question. Since maternal transfer of specific immune responses has been observed, breeding of animals on an antigen-free diet for several generations may be necessary to obtain immunologically naive animals. METHODS: To determine the most appropriate breeding conditions of mice to be used in immunological studies on food proteins, we examined immune responses towards beta-lactoglobulin (BLG) in mice bred on a milk-containing diet (F0) and then for three generations (F1-F3) on a commercially available milk-free diet. The specific antibody and cell-proliferative response to BLG was compared in non-immunized and immunized BALB/c mice, and in mice orally tolerized to BLG prior to immunization. RESULTS: The immune response to BLG in the F1 generation deviated from the response observed in the F0 and F2/F3 generations. Importantly, trace amounts of BLG detected in the commercial milk-free diet did not induce oral tolerance. CONCLUSIONS: The study showed that breeding mice on an antigen-free diet for at least two generations is required to attain animals appropriate for immunological studies of food proteins. Although the small quantity of BLG in the milk-free diet did not induce detectable oral tolerance in the present study, it is strongly recommended that the potential effect of contaminating dietary antigen is considered in future studies on food proteins.

Experimental parameters differentially affect the humoral response of the cholera-toxin-based murine model of food allergy.

BACKGROUND: Recent studies have developed a murine model of IgE-mediated food allergy based on oral coadministration of antigen and cholera toxin (CT) to establish a maximal response for studying immunopathogenic mechanisms and immunotherapeutic strategies. However, for studying subtle immunomodulating factors or factors effective during response initiation, this maximal response-based model is less suitable due to a lack of sensitivity. Therefore, in attempts to identify essential parameters to fine-tune the immune response towards a submaximal level, potentially more sensitive, we were interested in characterizing the individual effects of the parameters in the CT-based model: CT dose, antigen type and dose, and number of immunizations. METHODS: BALB/c mice were orally sensitized weekly for 3 or 7 weeks with graded doses of CT and various food antigens (soy-trypsin inhibitor, ovalbumin or ovomucoid). Antigen-specific IgG1, IgG2a, IgA and IgE were monitored by ELISA. RESULTS: The CT dose exerted a clear dose-dependent effect on the antigen-specific antibody response whereas the antigen dose tended to affect the kinetics of the developing response. Both the intensity and kinetics of the antibody response depended on the type of antigen and number of immunizations. CONCLUSIONS: The critical parameters of the CT-based murine allergy model differentially control the intensity and kinetics of the developing immune response. Adjustment of these parameters could be a key tool for tailoring the response to submaximal levels rendering the model potentially more sensitive for evaluating the effect of subtle immunomodulating factors that would be lost in the maximal response-based model.

Immunotoxicity of nucleic acid reduced BioProtein--a bacterial derived single cell protein--in Wistar rats.

BioProtein is a single cell protein produced by a mixed methanotrophic and heterotrophic bacteria culture using natural gas as energy source, which has been approved for animal feed. BioProtein contains a large amount of nucleic acids making the product less suitable for human consumption, therefore, a nucleic acid reduced variant (NABP) has been developed by the manufacturer. The purpose of the present study was to establish the safety of NABP in a subchronic toxicity rat study. Groups of 10 male and 10 female Wistar rats were fed diets containing 0, 6, 12 or 24% NABP for 13 weeks. Feeding NABP induced a humoral immune response and proliferation of phagocytic cell lines, mainly macrophages. The humoral response involved induction of NABP specific IgM and IgG. The proliferation of phagocytic cells involved increase of the white blood cell count of all dosed female groups. Males showed the same tendency, although, not statistically significant (P=0.09). The subsets of cells identified as neutrophils and eosinophils were increased and lymphocytes decreased. The histopathological examination revealed histiocytosis and accumulation of foamy macrophages in the mesenteric lymph nodes, hyperplasia of Kupffer cells in the liver, increased granulopoiesis in spleen and bone marrow, and infiltration of lamina propria of the large intestine with eosinophilic granulocytes. The most consistent and pronounced changes were observed in the highest dose group, but even at the lowest dose level some of the changes were present. Accordingly, a no-observed-effect level could not be established based on this study.