Probiotics and prebiotics, alone or together (synbiotics), can influence the intestinal microbiota and modulate the immune response. They may therefore be tools that can prevent or alleviate certain pathologies involving the gut immune system, such as allergies for which no treatment is yet available. This review focuses first on the definitions of probiotics, prebiotics, and synbiotics and key cells in the gut immune system. It then discusses their effects on mucosal immune stimulation. Experimental findings suggest that different probiotic species have similar effects on innate immunity by improving the mechanisms of pathogen destruction. On the contrary, their impacts seem to be variable on the adaptive immune system. Prebiotics can also exert an influence on the gut immune system via the stimulation of the autochthonous bacteria metabolism. Finally, this review focuses on the effects of food supplements on allergy. Different studies performed in humans or rodents have supported a potential role for selected probiotics and prebiotics in reducing some allergic parameters. Probiotic effects on allergy treatment are unclear, especially in human studies. However, they are potentially effective at short-term for prevention when they are administered in perinatal conditions. A clinical study performed with an infant cohort revealed a beneficial effect of prebiotics in preventing allergic manifestations at long-term. Further studies are nonetheless essential to confirm these findings. Food supplements offer potential tools for the prevention or treatment of allergy, but insufficient evidence is available at present to recommend their use in clinical practice.

DG can sensitize mice much more efficiently than NG. Moreover, this mouse model of allergy to DG revealed an IgE reactivity pattern against purified gliadins which was very similar to that of DG-allergic patients.

Indoleamine 2,3-dioxygenase (IDO) is the first and rate-limiting enzyme of tryptophan catabolism through the kynurenine pathway. Intriguingly, IDO is constitutively and highly expressed in the mammalian epididymis in contrast to most other tissues where IDO is induced by proinflammatory cytokines, such as interferons. To gain insight into the role of IDO in the physiology of the mammalian epididymis, we studied both wild type and Ido1 ؊/؊ -deficient mice. In the caput epididymis of Ido1؊/؊ animals, the lack of IDO activity was not compensated by other tryptophan-catabolizing enzymes and led to the loss of kynurenine production. The absence of IDO generated an inflammatory state in the caput epididymis as revealed by an increased accumulation of various inflammation markers. The absence of IDO also increased the tryptophan content of the caput epididymis and generated a parallel increase in caput epididymal protein content as a consequence of deficient proteasomal activity. Surprisingly, the lack of IDO expression had no noticeable impact on overall male fertility but did induce highly significant increases in both the number and the percentage of abnormal spermatozoa. These changes coincided with a significant decrease in white blood cell count in epididymal fluid compared with wild type mice. These data provide support for IDO playing a hitherto unsuspected role in sperm quality control in the epididymis involving the ubiquitination of defective spermatozoa and their subsequent removal.Indoleamine 2,3-dioxygenase (IDO) 3 (EC 1.13.11.42) is the first and rate-limiting enzyme in Trp catabolism through the kynurenine pathway (Fig. 1). IDO is a ubiquitously expressed cytoplasmic protein typically activated by interferons (IFNs) (1-5). There is ample evidence that IDO mediates potent immunosuppression in classical immune responses as well as in fetal tolerance, tumor immune resistance, and regulation of autoimmune responses (1-3, 6 -8).Thirty years ago, Yoshida et al. (9) reported that rodent epididymal protein extracts exhibited a high IDO activity. Later, Takikawa et al. (10) demonstrated that unlike the classical cytokine-mediated expression of IDO encountered in nearly all mammalian tissues, the epididymal expression of IDO was constitutive and independent of IFN-␥. More recently, we have shown that IDO is expressed in a regionalized manner by both the principal and the apical cells of the most proximal epididymal region, the caput epididymis. To gain insights into the functions of IDO and the intermediates of the kynurenine pathway in the physiology of the mammalian epididymis, we measured the expression of IDO and related enzymes as well as the abundance of kynurenines and other Trp metabolites in both wild type (WT) and Ido1 Ϫ/Ϫ male mice. These data were correlated with light and electron microscopic analyses of epididymal epithelium, sperm count, sperm morphology, and fertility.

Pattern recognition receptors (PRRs) play a critical role in the detection of microorganisms and the induction of inflammatory and immune responses. Using PCR and Western-blot analysis, this study investigated the differential expression in the intestine of 14 PRRs and nine associated cytokines. Thirty-two pigs were used to determine the expression of these markers (1) along the proximal/distal axis of the small intestine (duodenum, jejunum, and ileum) and (2) between the intestinal segments and their respective lymphoid organs (Peyer's patches [PP] and mesenteric lymph nodes [MLN]). Six additional animals were used to quantify the expression of these genes along the crypt/villus axis of jejunum, using microdissected samples. Most genes showed increased expression (1) in the distal than in the proximal parts of the small intestine (TLR3, 5, RIG-I, IL-1β, IL-8, and IFN-γ); (2) in lymphoid organs (TLR1, 2, 6, 9, 10, IL-10, TNF-α), especially the MLN (TLR4, 7, 8, NOD1, NOD2, NALP3, IFN-α, IL-6, IL-12, and TGF-β), than in intestinal segments. The analysis along the crypt/villus identified: (1) genes with higher expression in lamina propria (TLR1, 2, 4, 9, NOD1, NOD2, IL-1β, IL-10, TGF-β, TNF-α) and (2) genes with higher expression in the villus (TLR3, 5, 6, RIG-I, IL-6). These results highlight the differential expression of PRRs and cytokines along the proximal/distal and the crypt/villus axis of the intestine, contributing to a fine analysis of the complex functional architecture of the small intestine and should be related to the gut microbiota.