Immunoregulation by probiotics

Probiotic bacteria may modulate innate immunity by maintaining intestinal epithelial barrier function, regulating APC function, or inducing immune tolerance. Probiotics with immunomodulatory functions or " immunoprobiotics" may benefit the host by priming immune readiness in the healthy state and suppressing pro-inflammatory tendencies in disease states. However, probiotic immunomodulation may depend on the activation or differentiation states of innate immune cells. Interestingly, probiotic-mediated immunosuppression may not require cell-to-cell contact; some may produce soluble factors that cross the intact epithelium and suppress inflammation in the host. Recent evidence suggests the possible application of probiotics for the treatment of inflammatory bowel disease, especially in the context of pouchitis. However, the paucity of feasibility studies highlights the need for more interventional trials and a greater mechanistic understanding of probiosis in animals and humans. This article will review the most recent literature describing how probiotics modulate host immunity, emphasizing Lactobacillus, and bringing to attention important concepts including how probiotics promote immune homeostasis.