CD4(+) T-cell activation is differentially modulated by bacteria-primed dendritic cells, but is generally down-regulated by n-3 polyunsaturated fatty acids.

Appropriate activation of CD4(+) T cells is fundamental for efficient initiation and progression of acquired immune responses. Here, we showed that CD4(+) T-cell activation is dependent on changes in membrane n-3 polyunsaturated fatty acids (PUFAs) and is dynamically regulated by the type of signals provided by dendritic cells (DCs). Upon interaction with DCs primed by different concentrations and species of gut bacteria, CD4(+) T cells were activated according to the type of DC stimulus. The levels of CD80 were found to correlate to the levels of expression of CD28 and to the proliferation of CD4(+) T cells, while the presence of CD40 and CD86 on DCs inversely affected inducible costimulator (ICOS) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) levels in CD4(+) T cells. For all DC stimuli, cells high in n-3 PUFAs showed reduced ability to respond to CD28 stimulation, to proliferate, and to express ICOS and CTLA-4. Diminished T-cell receptor (TCR) and CD28 signalling was found to be responsible for n-3 PUFA effects. Thus, the dietary fatty acid composition influences the overall level of CD4(+) T-cell activation induced by DCs, while the priming effect of the DC stimuli modulates CD80, CD86 and CD40 levels, thereby affecting and shaping activation of acquired immunity by differential regulation of proliferation and costimulatory molecule expression in CD4(+) T cells.

Whole-blood culture is a valid low-cost method to measure monocytic cytokines - a comparison of cytokine production in cultures of human whole-blood, mononuclear cells and monocytes.

Whole-blood and peripheral blood mononuclear cell (PBMC) cultures are used as non-validated surrogate measures of monocytic cytokine production. The aim of this investigation was to compare ex vivo cytokine production from human whole-blood and PBMC with that from isolated monocytes. We also assessed the intra- and inter-individual variation in cytokine production. In 64 healthy men (age 19-40 years) IL-6, TNF and IL-10 were measured by enzyme-linked immunosorbent assay in supernatants from whole-blood, PBMC and monocytes cultured 24 h with lipopolysaccharide (LPS) or UV-killed L. acidophilus. Cytokines produced from whole-blood was found to be more strongly correlated with monocytic cytokines than cytokines from PBMC, particularly after LPS-stimulation: r=0.57, P<0.001 versus r=0.33, P=0.01 for IL-6 and r=0.43, P<0.001 versus r=0.30, P=0.02 for TNF-alpha. Adjustment for a preceding 8-week dietary fatty acid-intervention did not change any of the associations. Based on measurements at three time-points 8 weeks apart the intra-individual variation was > or = 50% smaller than the inter-individual variation (P<0.05) in most whole-blood cytokine responses and LPS-stimulated IL-6 from PBMC. We conclude that whole-blood cultures are well-suited low-cost proxy-measures of monocytic cytokine production. Moreover, large inter-individual variation in cytokine production was demonstrated whereas the individual responses in whole-blood were reproducible even over long time-periods.

Fish oil supplementation of lactating mothers affects cytokine production in 2 1/2-year-old children.

n-3 PUFA influence immune functioning and may affect the cytokine phenotype during development. To examine whether maternal fish oil supplementation during lactation could modify later immune responses in children, 122 lactating Danish mothers with a fish intake below the population median were randomized to groups supplemented for the first 4 mon of lactation with 4.5 g/d of fish oil (equivalent to 1.5 g/d of n-3 long-chain PUFA) or olive oil. Fifty-three mothers with a fish intake in the highest quartile of the population were also included. The FA composition of erythrocyte membranes was measured at 4 mon and at 2 1/2 yr. Plasma immunoglobulin E (IgE) levels and cytokine production in lipopolysaccharide-stimulated whole-blood cultures were determined at 2 1/2 yr. Erythrocyte n-3 PUFA at 4 mon were higher in infants from the fish oil group compared with the olive oil group (P < 0.001) but were no longer different at 2 1/2 yr. The median production of lipopolysaccharide-induced interferon gamma (IFN-gamma) in the fish oil group was fourfold higher than that in the olive oil group (P = 0.034), whereas interleukin-10 (IL-10) production was similar. The IFN-gamma/IL-10 ratio was twofold higher in the fish oil group (P = 0.019) and was positively correlated with 20:5n-3/20:4n-6 in erythrocytes at 4 mon (P = 0.050). The percentages of atopic children and plasma IgE were not different in the two groups, but the study was not designed to look at atopy. Cytokine responses and erythrocyte FA composition in children of mothers with a high fish intake were intermediate in comparison with those in the randomized groups. Fish oil supplementation during lactation resulted in increased in vitro IFN-gamma production in the children 2 yr after the supplementation was given, which may reflect a faster maturation of the immune system.

Fish oil supplementation modulates immune function in healthy infants.

(n-3) PUFA influence immune function in adults and may also affect immune maturation during development. This randomized trial is, to our knowledge, the first to investigate whether fish oil supplementation in late infancy modifies immune responses. The study was a 2 x 2 intervention in 64 healthy Danish infants, who received cow's milk or infant formula alone or with fish oil (FO) (3.4 +/- 1.1 mL/d) from 9 to 12 mo of age. Before and after the intervention, fatty acid composition of erythrocyte membranes, plasma IgE, C-reactive protein, and soluble IL-2 receptor concentrations were measured. TNF-alpha, INF-gamma, and IL-10 concentrations in whole-blood cultures, stimulated for 22 h with LPS+phytohemaglutinin (PHA) or Lactobacillus paracasei, were also determined. IgA was measured in feces when infants were 10 mo of age. FO supplementation effectively raised erythrocyte (n-3) PUFA (P < 0.001), increased L. paracasei-induced INF-gamma (P = 0.05) and tended to reduce LPS+PHA-induced IL-10 (P = 0.08). The FO intervention did not affect any of the other analyzed immune variables. The erythrocyte content of eicosapentanoic acid was negatively associated with LPS+PHA-induced IL-10 (r = -0.38, P = 0.02). Feeding milk rather than formula did not affect cytokine production, but plasma soluble IL-2 receptor concentration was greater in the formula group than in the cow's milk group (P = 0.03). Since the capacity to produce INF-gamma has been proposed as a maturation marker for the immune system in early life, this study suggests a faster immune maturation with FO supplementation with no apparent reduction in immune activation. The implications for later health need further investigation.

Modulation of ovomucoid-specific oral tolerance in mice fed plant extracts containing lectins.

We investigated the effect of feeding extracts of four different legumes (red kidney bean (Phaseolus vulgaris), peanut (Arachis hypogaea), soyabean (Glycine max) and pea (Pisum sativum) on the specific immune response against a food protein. Mice were fed ovomucoid and the specific immune response was evaluated. Ovomucoid fed alone resulted in oral tolerance induction measured as both a reduced ovomucoid-specific spleen cell proliferation and antibody response. Feeding kidney-bean extract prevented induction of oral tolerance to ovomucoid measured as spleen cell proliferation in vitro. Pure kidney-bean lectin also prevented oral tolerance induction, suggesting that lectin in the kidney-bean extract caused inhibition of oral tolerance. Parenteral administration (intravenous and intraperitoneal) of pure kidney-bean lectin had no significant influence on oral tolerance induction. Soyabean extract also influenced the immune response against ovomucoid; however, this was not as pronounced as for kidney bean and was only significant (P<0.001) for the antibody response. No effect was observed when pea extract was fed and peanut extract had a non-significant effect on induction of oral tolerance and on the general immune response. Plasma antibodies against kidney-bean lectin, but not against the three other legume lectins, were detected. Our current findings show that other dietary components can influence the specific immune response against food proteins. Various dietary components may thus contribute to the onset of adverse immunological responses.

Low-dose oral tolerance due to antigen in the diet suppresses differentially the cholera toxin-adjuvantized IgE, IgA and IgG response.

BACKGROUND: Cholera toxin (CT) is used as a mucosal adjuvant amongst other applications for studying food allergy because oral administration of antigen with CT induces an antigen-specific type 2 response, including IgE and IgA production. Previously established oral tolerance due to antigen in the diet may radically impact on the CT-adjuvantized immune response. The present study served to evaluate the effect of previously established low-dose oral tolerance on the CT-adjuvantized immune response towards a food antigen. METHODS: Mice fed a diet containing microgram levels of the soy protein Kunitz soy-trypsin inhibitor (KSTI) (F0 mice) and mice fed a soy-free diet (F2 mice) were orally immunized with KSTI and CT. KSTI-specific serum IgG1, IgG2a, IgA and IgE and fecal IgA were monitored. KSTI-stimulated cell proliferation and interleukin (IL)-6 production were determined. RESULTS: The anti-KSTI IgE and IgA responses in the F0 mice were substantially suppressed, while the IgG1 and IgG2a responses were not suppressed after five oral immunizations. The response suppression tended to decline with increasing numbers of immunizations suggesting that the suppression could be overcome by multiple immunizations. However, cell proliferation and IL-6 production were clearly suppressed even after five immunizations. CONCLUSIONS: Priorly established low-dose oral tolerance considerably suppressed the CT-adjuvantized KSTI-specific IgE, IgA and cellular immune response but only weakly and transiently the IgG response. The results revealed that low-dose oral tolerance includes the mucosal IgA response and that CT, albeit mediating an antigen-specific response, does not fully abrogate previously established oral tolerance.

Lipopolysaccharide contamination of beta-lactoglobulin affects the immune response against intraperitoneally and orally administered antigen.

BACKGROUND: Microbial components in the environment are potent activators of the immune system with capacity to shift the active immune response towards priming of Th1 and/or Th2 cells. Lipopolysaccharide (LPS), a cell-wall component of Gram-negative bacteria, is extensively present in food products like cow's milk. It is not well established, however, how this presence of LPS affects oral tolerance induction. METHODS: We studied the effect of LPS contamination in a commercial preparation of the cow milk protein beta-lactoglobulin (beta-LG) on antigen-specific immune responses. IgG1/IgG2a production upon intraperitoneal immunization without adjuvant was measured, and oral tolerance induction against beta-LG after administration of either an aqueous solution or water-in-oil (w/o) emulsion of beta-LG was evaluated. RESULTS: LPS contamination of beta-LG provoked a beta-LG-specific IgG2a response, as well as an enhanced beta-LG-specific IgG1 response upon intraperitoneal immunization. Oral tolerance induction to beta-LG was induced by aqueous solutions of beta-LG with and without LPS administration. Conversely, oral administration of w/o-emulsified beta-LG prevented oral tolerance to beta-LG only when the beta-LG was contaminated with LPS. CONCLUSIONS: LPS contamination of an aqueous protein solution does not affect oral tolerance induction, whereas LPS present in emulsion prevents oral tolerance induction towards the food protein.