Immunoregulation by probiotic lactobacilli

Probiotic lactobacilli are able to transiently survive in the human gastrointestinal tract following oral delivery, where they may signal sentinel cells of the immune system (such as those expressing pattern recognition receptors). Recent evidence suggests that the form of immune signal is strongly strain-dependent, with some well-defined bacterial strains potentiating systemic T helper (Th) 1-type immune activity and favoring cell-mediated immunity (CMI). Clinical studies have shown promising outlets for the use of non-pathogenic lactobacilli as provisioners of pro-Th1 immune signals in anti-allergy and anti-tumor immunotherapy, as well as combating intracellular microbial infections and immunosenescence. The underlying process appears to involve pro-Th1 activating cytokines (IFNα/IFNγ, IL-12, and IL-18) generated following bacterial contact with accessory leukocytes. The utilization of pro-Th1/CMI lactobacilli in present and future clinical immunotherapy is discussed.