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

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Abstract
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‐γ 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.