Lactobacillus rhamnosus alters intestinal IgA levels and IgA–microbiota interactions in healthy mice in a strain-specific manner

Abstract

Immunoglobulin A (IgA), a mucosal immune antibody, exhibits different degrees of affinity to intestinal bacteria and performs a diverse range of immune functions. IgA secretion is closely related to microbial stimulation. The stimulation pathways and effects of pathogenic intestinal bacteria and probiotics are reported to be different. However, it is unclear whether the mode of action between probiotics, gut microbiota, and IgA in healthy hosts varies depending on strain differences. In this study, six different strains of Lactobacillus rhamnosus from humans were used to investigate the differences in their effects on IgA levels and the gut microbiota affinitive to IgA in the intestines of healthy mice. It was found that six strains of L. rhamnosus exerted different effects on IgA levels and IgA-coated bacteria in the intestines of healthy mice. Short-term administration of L. rhamnosus CCFM1228, 28L2 and W6L1 improved the secretion of intestinal IgA and the IgA index values for Escherichia–Shigella, Pseudomonas, and other potential pathogens. However, for other species in the intestinal, L. rhamnosus strains showed different trends in their regulatory effects. L. rhamnosus CCFM1228 decreased the affinity of IgA for Enterococcus and increased the IgA index values for Alistipes and Alloprevotella. But L. rhamnosus 66L1 and W6L1 significantly increased the affinity of IgA for Pseudomona. However, this change was not significantly correlated with caecal SCFA levels or colonic inflammatory factors. Finally, only L. rhamnosus 66L1, CCFM1228, and W6L1, which enhanced 1 week faecal IgA concentration, promoted the transcription level of ACIDA. This study helps to provide new insights into the effect of L. rhamnosus on the intestinal IgA level and IgA–microbiota interactions in the gut of healthy hosts, thus supporting the individualized selection of probiotics for immune intervention.