The present invention features compositions and methods for modulation of the mucosal immune system. The compositions include foods fermented by the probiotic organism, Lactobacillus paracasei CBA L74 (International Depository Accession Number LMG P-24778). Alternatively the compositions can include L. paracasei CBA L74 and a physiologically acceptable carrier. In some embodiments, the L. paracasei CBA L74 can be non-replicating. The compositions can be administered to a subject having or at risk for gastrointestinal disorders related to immaturity of the immune system, infection or disease.