Abstract
Commensal bacteria in the gut, which is the largest host immune tissue, are critical for the normal function of the mammalian immune system. The Bacteroides genus is one of the most predominant genera of bacteria in the human or murine intestine, with the characteristics and physiological functions of this genus having undergone much investigation in recent years. Intestinal bacteria affect the environment of their host intestine by utilizing the components of food consumed by the host and their metabolites. Bacteroides species metabolize fructooligosaccharides, including their main components, GF2 and GF3. Furthermore, it has been demonstrated that Bacteroides species exhibit immunomodulatory functions. The production of IgA by Peyer’s patch cells induced by Bacteroides species is more effective than that induced by Lactobacillus. In Bacteroides monoassociated mice, Bacteroides species promote IgA production in the large intestine by inducing germinal center formation and increasing the number of IgA+ B cells. The bacterial products, e.g., polysaccharide A, derived from Bacteroides species can modulate the T cell-dependent immune reaction for the development and homeostasis of the host immune system, including protection from pro-inflammatory responses. This review provides an overview of growth factors for Bacteroides and immunologic properties, including mechanisms of immune system activation and resulting immunomodulatory effects.
