Exopolysaccharide fraction from Pediococcus pentosaceus KFT18 induces immunostimulatory activity in macrophages and immunosuppressed mice

Aims: Exopolysaccharide fraction from Pediococcus pentosaceus KFT18 (PE-EPS), a lactic acid bacteria isolated from Kimchi (a Korean fermented vegetable product), was preliminary characterized and its immunostimulating effects were analysed. Methods and Results: In this study, we used interferon-γ (IFN-γ)-primed RAW 264·7 macrophages and CD3/CD28-stimulated splenocytes to determine the immunotimulatory activities of PE-EPS. Upon exposure to PE-EPS, IFN-γ-primed RAW 264·7 macrophages showed significant increases in the expressions of inducible nitric oxide synthase (iNOS), tumour necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β. Molecular data using reporter gene assay and electrophoretic mobility shift assay (EMSA) revealed that PE-EPS upregulated transcriptional activity, DNA binding and the nuclear translocation of nuclear factor-κB (NF-κB). Furthermore, PE-EPS enhanced anti-CD3/CD28-specific proliferation and the productions of IL-2 and IFN-γ in primary splenocytes. In cyclophosphamide-induced immunosuppressed mice, pretreatment with PE-EPS (5, 15 or 45 mg kg^-1 day^-1, p.o.) increased thymus and spleen indices, and improved lymphocyte and neutrophil counts. Conclusion: PE-EPS stimulated the IFN-γ-primed macrophages and primary splenocytes to induce immune responses and improved the cyclophosphamide-induced immunosuppression in mice. Significance and Impact of the Study: The results in this study improved our understanding of immunostimulating activity of PE-EPS and supported its potential treatment option as a natural immunostimulant.