Intestinal immunomodulatory activity of indigestible glucan in mice and its utilization by intestinal bacteria in vitro

Comparison of the effects of three forms of soluble dietary fiber on the production of IgA in BALB/cAJcl and BALB/cAJcl-nu/nu mice

BACKGROUND

Their ability to induce the production of IgA, especially in the intestine, is one of the health benefits of soluble dietary fibers (SDFs), but the mechanism involved is unclear.

OBJECTIVE

This study was designed to identify the relationship between the induction of IgA by SDFs and the cecal short-chain fatty acids (SCFAs) content, and to evaluate the importance of T cell-independent IgA production for SDF-induced IgA production.

METHODS

We compared the SDFs fructooligosaccharides (FO), indigestible glucan (IG), and polydextrose (PD). Male BALB/cAJcl mice or T cell-deficient BALB/cAJcl-nu/nu (nude) mice were fed diets supplemented with one SDF (3% w/w) for 10 weeks and we measured IgA content in their feces, plasma, lung, and submandibular gland.

RESULTS

In BALB/cAJcl mice, the consumption of all three SDF diets induced fecal IgA production, but the response was stronger in the IG and PD groups than in the FO group. The IgA concentration of the plasma and lung were also higher in the FO and PD groups, and these groups showed significantly higher cecal acetic and n-butyric acid content. In contrast, in nude mice, the induction of IgA production was identified only in fecal samples of mice fed the three SDF diets, even though there were significant increases in cecal SCFAs content.

CONCLUSIONS

The induction of IgA production by SDFs is occurred T cell-independently in the intestine, but that in the plasma, lung, and submandibular gland is T cell-dependent. SCFAs generated in the large intestine might influence the systemic immune system, but there is no clear relationship between the generation of SCFAs and intestinal IgA production in response to SDF consumption.