Neuromyelitis optica (NMO)-IgG/AQP4-Ab as detected by an M23-DNA-AQP4-based, cell-based assay (CBA) and an M1-AQP4-DNA-based CBA with leaky scanning (LS). M23-AQP4-DNA-transfected cells (A), M1- AQP4-DNA-transfected cells with LS (B) and mock-transfected cells (C) were incubated in the same well on separate biochips. Note the higher signal intensity observed in the M23-AQP4-DNA-based assay in a direct comparison with the M1-AQP4-DNA-based assay observed with this particular sample (NMO#1). Panel D and E show results obtained with serum from a healthy control donor. Photographs were taken with a Nikon Ni-E upright, wide-field, research microscope using identical exposure times and camera settings. Binding of NMO-IgG/AQP4-Ab was visualized using a FITC-labeled anti-human IgG antibody. FITC = fluorescein isothiocyanate; HC = healthy control.