Leuconostoc citreum(L. citreum) HJ-P4 (KACC 91035) is one of the major predominant species in kimchi fermentation in Korea. The purpose of the present study was to test the immunomodulatory capacity ofL. citreumto modulate the IgE-mediated allergic response and to examine the involvement of NF-κB and MAPK in IL-12 production in macrophages. Balb/c mice were sensitized with OVA/alum and oral administration ofL. citreumto the mice began before or after the OVA sensitization. Protein and mRNA expression of Th1 cytokines in splenocytes byL. citreum in vitrowas measured. The role of NF-κB and MAPK such as p38, ERK1/2 and JNK inL. citreum-induced IL-12 was investigated in peritoneal macrophages and RAW264.7 cell lines.L. citreuminhibited the serum levels of total IgE, IgG1 and IgG2a altogether and increased OVA-specific IFN-γ production in splenocytes from pre- and post-sensitized animals. However, the downregulation of IL-4 and IL-5 production was observed only in the pre-sensitization group. The ability ofL. citreumto stimulate IFN-γ was dependent on its induction of IL-12. NF-κB, p38 and JNK were mainly involved inL. citreum-induced IL-12 production. In conclusion, the current study demonstrated thatL. citreumis able to regulate serum IgE generation at the induction and effector phases of allergic response through overall control over antibody production and that its involvement of IL-12 production was mediated through NF-κB and p38/JNK. Taken together, the use ofL. citreumcan be useful in preventing the development and progression of IgE production.