Probiotics And Immunomodulation

Páginas: 27 (6575 palabras) Publicado: 19 de octubre de 2012
Probiotics: effects on immunity1–3
Erika Isolauri, Yelda Sütas, Pasi Kankaanpää, Heikki Arvilommi, and Seppo Salminen
ABSTRACT The gastrointestinal tract functions as a barrier against antigens from microorganisms and food. The generation of immunophysiologic regulation in the gut depends on the establishment of indigenous microflora. This has led to the introduction of novel therapeuticinterventions based on the consumption of cultures of beneficial live microorganisms that act as probiotics. Among the possible mechanisms of probiotic therapy is promotion of a nonimmunologic gut defense barrier, which includes the normalization of increased intestinal permeability and altered gut microecology. Another possible mechanism of probiotic therapy is improvement of the intestine’simmunologic barrier, particularly through intestinal immunoglobulin A responses and alleviation of intestinal inflammatory responses, which produce a gut-stabilizing effect. Many probiotic effects are mediated through immune regulation, particularly through balance control of proinflammatory and antiinflammatory cytokines. These data show that probiotics can be used as innovative tools to alleviateintestinal inflammation, normalize gut mucosal dysfunction, and down-regulate hypersensitivity reactions. More recent data show that differences exist in the immunomodulatory effects of candidate probiotic bacteria. Moreover, distinct regulatory effects have been detected in healthy subjects and in patients with inflammatory diseases. These results suggest that specific immunomodulatory properties ofprobiotic bacteria should be characterized when developing clinical applications for extended target populations. Am J Clin Nutr 2001;73(suppl):444S–50S. KEY WORDS Allergy, gastrointestinal tract, immune response, infants, inflammation, probiotics, antigen, lymphocytes, microflora and the activation of secretion, motility, and absorption (2). During postnatal development, further maturational andadaptive events in the gut defense barrier include the appearance of mucosal proteins and digestive enzymes and the development of the intestinal flora. Gastric acidity is an important defense against microorganisms and secretion of hydrochloric acid by gastric mucosa develops during the first months of life (3). Goblet cell mucus that covers the epithelial surface of the gastrointestinal tract is animportant physical barrier that interferes with intestinal attachment of luminal antigens. The establishment of normal bacterial populations can prevent overgrowth of potential pathogens in the gastrointestinal tract. Maturational changes also affect the epithelial cell membranes, a major mechanical interface between the internal environment of the host and the luminal contents. It was shown inexperimental animals that postnatal maturation of small intestinal brush border membranes is associated with increased food-protein binding capacity (4). The capacity of antigens to bind to epithelial cells is related to the rate and route of antigen transfer and is shown to influence the intensity of mucosal immune responses (5).

Downloaded from ajcn.nutrition.org by guest on September 28, 2012ROLE OF GUT MUCOSAL BARRIER IN HOST DEFENSE The primary role of the gastrointestinal tract is to digest and absorb nutrients to meet the metabolic requirements and demands for normal human growth and development. In addition, the intestinal mucosa provides a protective host defense against the constant presence of antigens from food and microorganisms in the gut lumen. Protection againstpotentially harmful agents is ensured by many factors, including saliva, gastric acid, peristalsis, mucus, intestinal proteolysis, intestinal flora, and epithelial cell membranes with intercellular junctional complexes (1). An abrupt change in gut barrier function occurs at birth when the gut switches from processing amniotic fluid to digesting milk. Food consumption initiates the release of trophic...
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