Effects of intestinal microflora on host immune mechanism

Abstract

Lactic acid bacteria (LAB) in intestinal flora are useful in maintaining good health. Recently, it has been reported that LAB act on the immune mechanism and increase the body's resistance to infection, cancer and allergy. In this paper, it was showed that oral administration of Bifidobacterium breve YIT4064 (B. breve) to mice activated the humoral immune system, augmented anti-rotavirus IgA production or anti-influenza virus (IFV) IgG production and protected against rotavirus infection or influenza infection, respectively. Furthermore, when the B. breve was given to infants, there was a significant reduction of the frequency of rotavirus shedding in stool samples during the administration of the bacteria. It was also found, again using mice, that oral administration of Lactobacillus casei strain Shirota (LcS) stimulated type 1 helper T (Th1) cells, activated the cellular immune system, inhibited incidences of tumors, influenza infection and IgE production. In the human study, it was demonstrated that oral administration of LcS into surgical operated patients suppressed the recurrence of superficial bladder cancer in a double-blind clinical trial. On the basis of both our data and the data of other authors, it was showed that some strains of Bi adobacterium and Lactobacillus had immunomodulatory activities and were able to protect against various diseases .