Peptidoglycan from Bifidobacterium bifidum G9-1 induces IgA secretion in Peyer's patch-derived cells

Sep 29, 2026

Peptidoglycan (PG) from the probiotic Bifidobacterium bifidum G9-1 (BBG9-1) was evaluated for its ability to induce IgA secretion in Peyer’s patch (PP)-derived cells. Heat-killed BBG9-1, but not its culture supernatant, significantly enhanced IgA secretion and promoted cell aggregation. Compared with other Gram-positive bacteria, BBG9-1 showed stronger IgA-inducing activity, and component analysis identified PG as the key driver, while lipoteichoic acid was not stimulatory. These results support PG as a candidate for modulating mucosal immune responses.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

Background

IgA functions in mucosal immunity

Prior evidence from beneficial bacteria and BBG9-1

Bioscience of Microbiota, Food and Health Vol. 45 (1), 79–83, 2026 Note Peptidoglycan from Bifidobacterium bifidum G9-1 induces IgA secretion in Peyer’s patch-derived cells Hiroaki KONISHI1, Koji YAMAMOTO2, Aki SAKATANI3, Tatsuya DOKOSHI3, Yutaka MAKIZAKI4, Yoshiki TANAKA4, Hiroshi OHNO4, Kentaro MORIICHI3 and Mikihiro FUJIYA1, 3* 1Department of Gastroenterology and Advanced Medical Sciences, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido 078-8510, Japan 2Department of Physiology, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido 078-8510, Japan 3Division of Gastroenterology, Department of Internal Medicine, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido 078-8510, Japan 4Biofermin Pharmaceutical Co., Ltd., 7-3-4 Higashi-machi, Ibukidai, Nishi-ku, Kobe, Hyogo 651-2242, Japan Received June 11, 2025; Accepted September 11, 2025; Published online in J-STAGE December 18, 2025 Immunoglobulin A (IgA) plays a key role in mucosal immunity. We investigated the IgA-inducing capacity of heat-killed Bifidobacterium bifidum G9-1 (BBG9-1) using Peyer’s patch (PP)-derived cells. Heat-killed BBG9- 1, but not its culture supernatant, significantly enhanced IgA secretion and cell aggregation. Compared with other Gram-positive bacteria, BBG9-1 showed a stronger IgA-inducing effect. Component analysis revealed that peptidoglycan (PG), but not lipoteichoic acid (LTA), isolated from BBG9-1 significantly stimulated IgA secretion. These findings suggest that PG from BBG9-1 is a key factor in IgA induction, supporting its potential application in modulating mucosal immune responses. Key words: immunoglobulin A, Bifidobacterium bifidum G9-1, peptidoglycan Immunoglobulin A (IgA) plays a crucial role in maintaining homeostasis by regulating gut microbiota and strengthening the intestinal barrier within the mucosal immune system [1]. Secretory IgA, the predominant form in mucosal secretions, facilitates immune exclusion by preventing pathogen adhesion to epithelial surfaces and neutralizing toxins [2] . IgA modulates the microbiota composition by selectively coating specific bacteria, fostering the expansion of beneficial commensals while suppressing potential pathogens [3] . Elevated IgA levels also enhance mucosal barrier integrity by reinforcing tight junctions, thereby reducing gut permeability and limiting systemic inflammation [4] . Beneficial bacteria, such as Lactobacillus and Bifidobacterium species, can stimulate IgA production via interactions with intestinal epithelial and antigen-presenting cells [5]. These bacteria activate dendritic cells and other immune cells to differentiate B cells into IgA-secreting plasma cells, thereby enhancing mucosal immunity [6]. Additionally, metabolites derived from beneficial bacteria, such as short-chain fatty acids, modulate IgA responsesand promote gut immune homeostasis [7] . However, the extent to which individual strains vary in their IgA-inducing capacity and the specific bacterial components—such as surface proteins, polysaccharides, and secreted metabolites—responsible for this activity remain unclear. Bifidobacterium bifidum G9-1 (BBG9-1) is a probiotic strain known to maintain the intestinal microbiota balance and exert various immunomodulatory effects. Previous investigations have demonstrated that BBG9-1 reduces total and antigen-specific IgE levels in ovalbumin-sensitized mice, suggesting potential antiallergic effects [8] . It also enhances the expression of antiinflammatory cytokines such as interleukin-10 and transforming growth factor-beta (TGF-β), as well as the regulatory T cell marker forkhead box P3 [9] . Furthermore, BBG9-1 has shown efficacy in alleviating symptoms of low-fiber diet-induced constipation and drug-induced diarrhea [10, 11] . However, its influence on intestinal IgA secretion remains to be elucidated. In this study, we evaluated the ability of heat-killed

FAQs

What is the main purpose of the study?

To determine whether peptidoglycan from Bifidobacterium bifidum G9-1 can induce IgA secretion in Peyer’s patch-derived cells.

How did heat-killed BBG9-1 compare with its culture supernatant?

Heat-killed BBG9-1 significantly enhanced IgA secretion and cell aggregation, whereas the culture supernatant did not.

Which bacterial component was identified as responsible for IgA induction?

Peptidoglycan (PG) isolated from BBG9-1 stimulated IgA secretion, while lipoteichoic acid (LTA) did not.

Sep 29, 2026

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