Bifidobacterium longum subsp. Infantis modulates intestinal immunity in growing mice in a strain-specific manner

The early life period is a critical phase for the colonization of initial gut microbes in infants, during which the immune system develops and matures. These processes have long-lasting implications that may extend into adolescence and even adulthood. Bifidobacterium longum subsp. infantis, recognized as an ideal probiotic during infancy, has the potential to modulate intestinal immunity and mitigate immune-mediated diseases. This research explored the potential of various B. longum subsp. infantis strains to modulate the balance between T helper (Th)1 and Th2 responses, immune cell populations, Immunoglobulin A (IgA), and the related genes expression in mice. Notably, B. longum subsp. infantis FHNFQ4M11 and CCFM1269 demonstrated more robust regulatory capabilities. These two strains, which exhibited higher ILA production, activated the aryl hydrocarbon receptor (AHR) signaling pathway, upregulated the levels of galectin-1 (Gal-1) and galectin-3 (Gal-3), and modulated Th1/Th2 differentiation markers in the colon. Additionally, these strains significantly elevated IgA concentrations in both serum and colon and modulated the gut microbiota composition. These findings underscored the potential of specific B. longum subsp. infantis strains as targeted probiotic interventions in early life, providing a promising strategy for promoting immune homeostasis and gut health in infants.