Lactobacillus plantarum exopolysaccharides exert immunomodulatory function by regulating Th1 and Th2 responses in mice.

Abstract

Background: Our previous study demonstrated that exopolysaccharides (EPS) from Lactobacillus plantarum (L. plantarum) act as an effective adjuvant. They can enhance both the immune response elicited by the oprH recombinant subunit vaccine against Pseudomonas aeruginosa (P. aeruginosa) and the protective efficacy in experimental animals. However, it is not clear whether oral administration of L. plantarum EPS can promote immune function in experimental animals.

Aims: The present study aimed to explore the immunoregulatory function of L. plantarum EPS in mice.

Methods: EPS was extracted from L. plantarum. EPS was then orally administered to the mice at doses of 20, 40, and 60 mg/kg for 20 consecutive days. After 10 and 20 days, the immune organ index, delayed-type hypersensitivity (DTH), phagocytic ability of peritoneal macrophages, serum hemolysin, and splenic lymphocyte proliferation of mice were measured. The concentrations of IgG1, IgG2a, IFN-γ, IL-2, IL-4, and IL-10 in serum were measured using ELISA. The percentage of CD4⁺ and CD8⁺ T lymphocytes subpopulations and the expression of transcription factors T-bet and GATA-3 in the mouse spleen cells were measured by flow cytometry and qRT-PCR, respectively.

Results: L. plantarum EPS could induce high levels of immune organ index, DTH reaction, phagocytic ability of peritoneal macrophages, serum hemolysin, splenic lymphocyte proliferation, serum IgG1, IgG2a, Th1-type cytokines IL-2, IFN-γ, Th2-type cytokines IL-4, IL-10, CD4⁺ T lymphocyte, CD8⁺ T lymphocyte, T cell transcription factors T-bet and GATA-3, and has a certain dose-dependency.

Conclusion: L. plantarum EPS can concurrently upregulate both Th1 and Th2 immune responses in mice, with this effect being more pronounced, particularly at the high dose. Our study provides a theoretical basis for research on L. plantarum EPS in veterinary.