Effects of lysed Enterococcus faecalis FK-23 on allergen-induced serum antibody responses and active cutaneous anaphylaxis in mice

BACKGROUND: Our previous studies have presented evidence that lysed Enterococcus faecalis FK-23 (LFK), a lysozyme and heat-treated probiotic product, can inhibit allergen-induced local accumulation of eosinophils in mice. OBJECTIVE: The purpose of this experimental study was to evaluate the influence of orally administrated LFK on the host immune responses. METHODS: BALB/c mice were sensitized subcutaneously, and challenged intraperitoneally by cedar pollen allergen. Blood and spleen samples were collected after oral administration of LFK 60 mg/day for 21 days. The serum levels of total and allergen-specific IgE and IgG2a antibodies and the production of IL-4, IL-5 and IFN-gamma generated by allergen-stimulated cultured splenocytes were determined. Additionally, the effect of LFK on active cutaneous anaphylaxis (ACA) induced by ovalbumin (OVA) challenge in mice was measured after 28 days LFK treatment. RESULTS: No significant differences in serum immunoglobulin levels, as well as in cytokine production of splenocytes were observed between LFK-treated and control mice (P>0.05). There was, however, an increasing tendency of allergen-specific IgG2a level in mice after LFK treatment for 21 days compared with controls (P=0.060). Furthermore, the serum ratio of specific IgE to IgG2a was found to be significantly decreased in the LFK group (P=0.005). In addition, a significant inhibition of OVA-induced ACA reaction was observed in mice that had been fed for 28 days with LFK compared with control mice (P=0.008). CONCLUSION: These results suggest that LFK shows an anti-inflammatory effect, which may be part of the mechanism for protection against IgE-mediated allergy.