Pectin oligosaccharide influences gut microbiome
Immunoglobulin A (IgA) is an important factor to maintain homeostasis at mucosal surfaces. Levels of luminal IgA can vary widely; the current dogma suggests individual immune responses to specific microbes drive the overall IgA level. Here, we found the prebiotic, pectin oligosaccharide (pec-oligo), induced high-IgA levels in the small intestine in a T cell-dependent manner. Surprisingly, this IgA-high phenotype was retained after cessation of pec-oligo treatment and was readily transmissible by bacteria both horizontally and vertically in the absence of pec-oligo. Interestingly, we noted a mismatch comparing the bacterial taxa that were enriched in the overall pec-oligo bacterial community versus the IgA-coated microbes in this same community. We found a small group of ethanol-resistant microbes, highly enriched for Lachnospiraceae bacterium A2, drove the IgA-high phenotype. Our findings support a new model of intestinal adaptive immunity in which a limited number of microbes can promote durable changes directed to many symbionts.