title: Lactococcus strains treated with heat and hen-egg-white lysozyme induce abundant interleukin-12 production by J774.1 macrophages and murine spleen cells.
abstract: The IL-12-inducing ability of lactic acid bacteria could be a critical index of immunomodulatory activity, especially in promoting T-helper-1 responses and in suppressing T-helper-2-mediated allergic responses. We aimed to develop a simple method for enhancing the IL-12-inducing ability of bacteria. We examined the in vitro effects of strains of lysozyme-modified Lactococcus (ML-LYS), prepared by heat treatment of the Lactococcus strain in the presence of lysozyme, on the ability of mouse macrophage-like J774.1 cells and spleen cells to produce IL-12. An IL-12-inducing ability greater than that of heat-killed bacteria was shown by 41 of 46 ML-LYS strains in J774.1 cells and by all 46 ML-LYS strains in mouse spleen cells. In contrast, bacteria modified by α-lactalbumin, β-lactoglobulin, or ovalbumin did not enhance IL-12 production in J774.1 cells. Microscopically, ML-LYS showed stronger resistance to lysozyme and macrophage digestion than did heat-killed bacteria or the other modified bacteria. Addition of chitotriose, a lysozyme inhibitor, enhanced IL-12 production by J774.1 cells stimulated with heat-killed bacteria. Therefore, enhancement of resistance to lysozyme may be a key factor in the strong IL-12-inducing ability of ML-LYS. These findings have important implications for the design of dairy products that have an immunomodulatory effect using the modified bacteria.
authors.affiliation: National Institute of Livestock and Grassland Science, Ikenodai 2, Tsukuba, Ibaraki 305-0901, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Aoki
authors.forename: C
authors.initials: C
authors.lastname: Suzuki
authors.forename: H
authors.initials: H
authors.lastname: Kimoto
authors.forename: M
authors.initials: M
authors.lastname: Nomura
authors.forename: K
authors.initials: K
authors.lastname: Mizumachi
mesh_terms: D000818:Animals; D005260:Female; D006358:Hot Temperature; D018664:Interleukin-12 / Q000096:biosynthesis*; D017045:Lactococcus / Q000145:classification / Q000187:drug effects / Q000201:enzymology*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009113:Muramidase / Q000494:pharmacology*; D013154:Spleen / Q000166:cytology*
chemical_list: D018664:Interleukin-12; C421864:hen egg lysozyme; D009113:Muramidase