How can we impact the immune system with pre- and probiotics?

In recent years there has been a growing interest in understanding the influence of intestinal microbiota on the physiology of the body. Moreover, with the available genomic studies, it is now possible to analyze how components of the intestinal microbiota modulate features of human postnatal development and physiology [1]. An area of major interest has been the relationship between the gut bacteria and the immune system, both at the intestinal and systemic level [2]. Changes in the microbiologic content of the intestine can be induced by the administration of selected bacterial inoculums as part of a normal diet or as dietary supplements. The health-promoting microorganisms are called probiotics. The administration of specific fibers in the diet called prebiotics can also modify the intestinal ecology by promoting the growth of some particular components of the intestinal microbiota, such as bifidobacteria. On the one hand, there is an immune activation which is associated with improved mucosal defenses against pathogens and responses to oral vaccines. On the other, a modified immune reactivity which preserves homeostasis in mucosal tissues confronted with a constantly changing environment. Not only does the latter avoid an excessive reaction and inflammatory damage in the local environment, it also influences the homeostasis of the systemic immune system and prevents the development of allergic or autoimmune diseases. It is difficult to provide a simple mechanistic explanation for the underlying cellular and molecular events that support these apparently opposing effects. However, a brief overview of the evolving models that have been postulated to explain basic immune function, may help us understand how intestinal bacteria effect the mucosal and systemic immune systems [3, 4]. The most important of these are the following. Lochs H, Thomas DR (eds): Home Care Enteral Feeding. Nestlé Nutrition Workshop Series Clinical & Performance Program, vol 10, pp 203–217, Nestec Ltd., Vevey/S. Karger AG, Basel, © 2005.