High doses of the galactooligosaccharides, 2'-fucosyllactose alleviate immunodeficiency in vitro and in vivo.

Purpose: Galactooligosaccharides (GOS) are widely added to infant formula milk powder. One of these, 2'-fucosyllactose (2'-FL), has many potential applications. This study investigated the immunomodulatory effects of GOS and 2'-FL, alone or in combination, on RAW 264.7 cells, and their impacts on cyclophosphamide (CTX)-induced immunodeficiency in mice.

Methods: We used lipopolysaccharide (LPS)-treated RAW 264.7 cells and CTX-induced immunodeficient model mice to analyze the effects of GOS, 2'-FL, and the combination GOSFL on apparent indicators, cellular immunity, inflammation, intestinal barrier function, and the gut microbiota and its metabolites.

Results: In vitro, GOS and 2'-FL promoted cell proliferation and nitric oxide production, and exhibited dose-dependent increases in the secretion of interleukin-10 (IL)-10, IL-6, and tumor necrosis factor-α. In vivo, high-dose administration GOS, 2'-FL, or GOSFL reduced the body weight and spleen index of immune-deficient mice, increased the number of splenic immune cells, alleviated inflammation, and promoted the expression of Occludin, ZO-1, and MUC2 to restore the intestinal mucosal barrier. GOS and 2'-FL each increased the relative abundances of Bacteroidota and Muribaculaceae, while decreasing those of Firmicutes, Lachnospiraceae, and Lactobacillaceae. Spearman correlation analysis revealed correlations between the gut microbiota and serum immune factors, as well as short-chain fatty acids.

Conclusion: GOS and 2'-FL significantly promoted cytokine secretion in vitro. High doses of GOS or 2'-FL in vivo reversed the adverse effects induced by CTX, modulated the gut microbiota, and boosted the immune response, with combination use producing similar effects.