GEM preparation
L. lactis MG1363 cultured in M17 medium was centrifuged to obtain the bacteria. After washing once with sterile distilled PBS, the bacteria were boiled for 30 min with 10% trichloroacetic acid (TCA) to obtain GEM particles. After washing three times with PBS, the number of GEM particles was counted using a C-Chip Burker Turk Hemocytometers (IN-Cyto, Chungnam-do, Korea), diluted to one unit (1 U, 2.5×109 particles per 1U) and stored at -70°C.