Lactic acid bacteria as immunomodulators of the gut associated immune system.

MALDONADO GALDEANO, CAROLINA; DE MORENO DE LEBLANC, ALEJANDRA; DOGI, CECILIA; PERDIGÓN, GABRIELA

Biotecnology of lactic acid bacteria: Novel applications

Wiley- Blackwell

Año: 2010; p. 125 - 140

The use of lactic acid bacteria (LAB) as starter cultures in many food products has made necessary a rigorous selection of strains to have products with beneficial effects on the human health in addition to their nutritional contributions. Several studies have demonstrated that LAB stimulate the systemic and mucosal immune system. The knowledge of the involved mechanisms is needed to establish the scientific basis for the use of these microorganisms as immune adjuvants. Experimental studies in animal models have demonstrated that the supplementation with different LAB induced mucosa immune activation in the gut mediated by the increase in the numbers of both proinflammatory and regulatory cytokine producer cells, thus maintaining the intestinal homeostasis. LAB administration also showed a tendency to stimulate the Th2 response with production of systemic antibodies. In these responses the bacterial viability is an important condition to have a good stimulation of the intestinal immune system. LAB interact with the intestinal epithelial cell and their fragments or antigenic particles can be internalized by the epithelial cells. These probiotic bacteria or their fragments can also interact with the immune cells associated to the gut and to induce immune activation. Secretory IgA (S-IgA), one of the principal defense antibodies at the intestinal level, is increased with the administration of probiotic bacteria. The clonal expansion of T lymphocyte population in lamina propria of the small intestine is not induced, after the intake of these microorganisms. Probiotic bacteria activate mainly the innate immune response (macrophages and dendritic cells) through the increase in the expression of receptors involved in the antigen clearance and in the immune signaling. LAB do not induce specific antibodies against their own epitopes and Nuclear factor of activated T cells (NFAT)and Nuclear Factor kappa B (NF-kB)are the transcriptional factors involved in the immune stimulation. The results of different studies allow to conclude that the principal immune mechanism induced by probiotic LAB is the activation of the innate response and the reinforcement of the intestinal barrier, protecting the host against intestinal pathologies by increasing in the surveillance of the host.