The immunomodulatory and antiallergic effects of human colonized probiotics

The rate of allergy is increasing particularly among infants due to several factors reaching up to 30%. Several materials components have been implicated in the development and excessive activation of the immune system, acting as irritants and allergic agents. In several studies, in Mediterranean inhabitants with a specific diet, the prevalence of allergies in children was low, whereas dietary supplements in the Western and Mediterranean countries had a different role in the regulation of immune responses and in the reduction of allergic reactions. Probiotics have been associated with reduction of allergic reactions mostly by positive effect on T helper cells, regulatory T cells (Tregs), B cells and dendritic cells. Furthermore, probiotics existing in the human intestine can modulate the immune response and allergic reactions through downregulation of Th2-related responses (IgE, IL-4 and IL-5). They mostly exert anti-inflammatory and immunomodulatory properties by modulation of immune system components via hindering of various signaling pathways such as the NF-kappa B pathway, probably associated with changes in mitogen-activated protein kinases and pattern recognition receptors pathways. These microorganisms have also potential to inhibit the bacterial lipopolysaccharide attachment to the CD14 receptor, hence reducing the overall activation of NF-kappa B and proinflammatory cytokines production. Bifidobacterium and Lactobacillus species act through increase in proinflammatory (Th1) cytokines (INF-gamma, IL-12, IL-13, TNF-alpha and also IL-4 and IL-10), dendritic cells, CD4+FoxP3+ T cells, GATA-3 and intestinal barrier maturation, whereas decrease the Th2-mediated cytokines, IgA, IgE, IgG1, IL-4, IL-5 and IL-6, IL-13, airway reactivity, pulmonary eosinophilia. Furthermore, Clostridium butyricum could act by improvement of anaphylaxis symptoms and increase of sIgA and CD4+ CD25+FoxP3Treg cells. In this review, we assessed the recent evidence that confirms the role of probiotics compounds as an important factor in the safety of homeostasis and the development of allergic reactions through a complex set of metabolites and the immune cells. The employment and application of probiotics combined with immunotherapy approaches can be possibly effective in reducing allergic reactions and related therapeutic costs.