WB analysis of six mouse serum samples with 2D-PAGE of OMVs using broad pH range (3–10) gels for 1D. Scanned images of MemCode^TM-stained membranes and WB are shown in the left and right columns, respectively. Merged images are shown in the right columns. Different mouse serum samples, (A) OMV-1, (B) OMV-2, (C) OMV-3, (D) OMV-4, (E) OMV-5 and (F) OMV-6, were subjected to WB. OMV samples prepared from the same batch cultures were used to obtain OMV-1, -2 and -3 by immunization. Other OMV samples prepared from the same batch cultures were used to obtain OMV-4, 5 and -6 by immunization. Immunoreactive signals are denoted by arrows with spot numbers. Serum samples of OMV-1, -2, -3 and -4 were used at a dilution of 1:1000. Serum samples of OMV-5 and -6 were used at a dilution of 1:500.