Allergies are a world increasing health issue and most treatments are oriented to alleviate symptoms. Probiotics have several health benefits including the improvement of the immune system. In previous work we found that consumption of commercial probiotic fermented milk (PFM) significantly reduced specific-immunoglobulin (Ig) E in serum and lungs by increasing specific-IgG and controlled allergic response to ovalbumin (OVA) in an adult mouse respiratory allergy model. Here we continued our study determining the mechanism triggered in the gut by the PFM ingestion that influenced the results previously reported. Five groups of BALB/c mice were assessed: normal-control, basal (drinks PFM five days without OVA sensitisation), sensitisation-control (no PFM intake), previous and continuous-PFM administration. Allergen administration: 3 OVA injections (1% in PBS) followed by aerosols exposure for 7 days. We determined total secretory-IgA and cytokines in small intestine (SI) fluid; CD11b+, CD103+, IgA+ cells and cytokine producing cells in SI tissue. In lungs we analysed co-expression of CD4/interferon (IFN)-γ or CD4/interleukin (IL)-10, IgE+ cells and IL-12 production. Results: continuous intake of PFM increased the expression of CD103 marker and decreased CD11b and pro-inflammatory cytokines. Coexpression of CD4/IFN-γ was confirmed in lungs of animals that consumed PFM continuously. This group had a lower count of IgE+ cells and a higher concentration of IL-12. The consumption of PFM reinforces the mucosal barrier by increasing IgA+ cells and induces signalling from the intestine to the lungs by increasing the expression of CD103+ dendritic cells related to regulatory mechanisms. The results found in this work together with those previously reported demonstrated that the intake of PFM induces a clear balance towards the Th1 response, preventing the Th2 allergic response by controlling the previously reported IgE level. According to our model, the intake of PFM could be a good strategy to alleviate the development of allergies.

The advent of omic platforms revealed the significant benefits of probiotics in the prevention of many infectious diseases. This led to a growing interest in novel strains of probiotics endowed with health characteristics related to microbiome and immune modulation. Therefore, autochthonous bacteria in plant ecosystems might offer a good source for novel next-generation probiotics. The main objective of this study was to analyze the effect of Rouxiella badensis acadiensis Canan (R. acadiensis) a bacterium isolated from the blueberry biota, on the mammalian intestinal ecosystem and its potential as a probiotic microorganism. R. acadiensis, reinforced the intestinal epithelial barrier avoiding bacterial translocation from the gut to deep tissues, even after feeding BALB/c mice for a prolonged period of time. Moreover, diet supplementation with R. acadiensis led to increases in the number of Paneth cells, well as an increase in the antimicrobial peptide α defensin. The anti-bacterial effect of R. acadiensis against Staphylococcus aureus and Salmonella enterica serovar Typhimurium was also reported. Importantly, R. acadiensis-fed animals showed better survival in an in vivo Salmonella enterica serovar Typhimurium challenge compared with those that received a conventional diet. These results demonstrated that R. acadiensis possesses characteristics of a probiotic strain by contributing to the reinforcement and maintenance of intestinal homeostasis.

The thymus is a primary lymphoid organ in which T lymphocyte differentiation occurs. It is considered as an organ of the endocrine system and thus an endocrine gland that secretes hormones and other soluble factors controlling the production and maturation of T lymphocytes, and regulating the activity and the interactions of T cells in peripheral tissues. It exerts a clear influence on the development and maturation of the lymphatic system and in the mucosal and systemic immune response. Protein-energy malnutrition causes a significant impairment of the immune system (1) , being the thymus one of the most affected organs (2) . The administration of a probiotic fermented milk can recover the intestinal barrier, histological alterations and mucosal and systemic immune functions affected by undernutrition in a non-severe malnutrition mouse model (3) . This study was aimed to evaluate in the same model of malnutrition the effect of a probiotic fermented milk added to re-nutrition diet on the recovery of the thymus, analyzing histological and functional alterations caused by malnutrition. After weaning (21 days) mice were randomly divided in two control groups (well-nourished control group that received conventional balanced diet and malnourished control group) (4) and three test groups according to the dietary supplement received during re-nutrition period: milk, probiotic fermented milk or its bacterial free supernatant. Malnourished control group and mice from the three test groups were fed during 5 days with conventional diet, without restriction and after that, the malnourished period started and the animals received restricted food (25 % less than well-nourished control). The malnourished control group was not re-nourished and continued with restrained ingestion during all the experiment, while mice of the test groups, when lost 25 % of body weight compared to well-nourished mice, continued with the restrained ingestion, but supplemented with the dietary supplements: whole milk rehydrated 10 % wt/vol, probiotic fermented milk or its bacterial free supernatant. Probiotic fermented milk was the most effective re-nutrition supplement to improve the histology of the thymus, decreasing the cellular apoptosis in this organ, and recovering the percentage of CD4 + /CD8 -single positive thymocytes. Immature double positive thymocytes were increased in the malnourished control. The production of different cytokines in the thymus was increased in mice given probiotic fermented milk compared to mice that received others dietary supplement and malnourished control. The analysis of the macrophages and dendritic cells did not show significant variations comparing test and control groups. Mice given the bacterial free supernatant presented an improvement in the thymus similar to those that received milk. This is a first report demonstrating the beneficial effect of probiotic administration on thymus after a malnutrition period; which would be also responsible for the improvement of the mucosal and systemic immune response obse...