Immunomodulatory effects of Leuconostoc citreum EFEL2061 isolated from kimchi, a traditional Korean food, on the Th2 type-dominant immune response in vitro and in vivo

•LC2061 enhanced Th1 cytokine production under Th2 polarisation conditions.•Oral treatment of LC2061 to ovalbumin allergic mice reduced serum levels of total IgE.•LC2061 decreased the population of active splenic B cells. We isolated several novel Leuconostoc citreum (LC) strains from kimchi, a traditional Korean fermented food, and screened for potential probiotics that have immunomodulatory activity toward the hyperactive Th2 response. After screening, we chose the LC EFEL2061 strain for its ability to induce strong interleukin (IL)-12 expression in mouse macrophages. This strain enhanced interferon (IFN)-γ production by mouse splenocytes cultured under Th2 polarisation conditions. Oral administration of LC EFEL2061 to ovalbumin (OVA)-sensitised mice significantly reduced the serum level of total IgE, but not that of OVA-specific IgE. Spleens from the LC EFEL2061 group had fewer CD19(+)CD80(+) cells than the OVA group and more CD40(+)CD86(+) cells than the sham group. Thus, LC EFEL2061 strongly induced Th1 type cytokines in vitro and, when consumed, decreased the elevated total IgE in serum in OVA-sensitised mice, possibly by downregulating bystander B cell activation or by upregulating the activity of innate immune cells.