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

Lugar: USA; Año: 2009;

The safety and beneficial effects on human health of selected lactic acid bacteria (LAB) used as probiotics in many food products need to be assessed by rigorous criteria. Several studies have shown that LAB stimulate the systemic and mucosal immune systems. To establish the scientific basis for the use of these microorganisms as immune adjuvants, the elucidation of the involved mechanisms is needed. Animal model studies have demonstrated that mucosa immune activation by different LAB is mediated by the increase in the numbers of proinflammatory and regulatory cytokine producing cells in the gut, thus maintaining the intestinal homeostasis. LAB administration also showed a tendency to stimulate the Th2 response with production of systemic antibodies, bacterial viability being an important condition. Probiotic LAB can interact with epithelial cells as well as with the immune cells associated with the gut to induce immune activation; microbial cells or their cellular fragments can also be internalized by the epithelial cells. Secretory 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, however, not induced by LAB. These 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 as well as the reinforcement of the intestinal barrier, thus protecting the host against intestinal pathologies.