Serum MOG-IgG mediated complement activation. A. High-titer MOG-IgG antibodies of an ADEM patient (titer 1:20,480) can activate the complement system on MOG expressing HEK-293A cells (MOG-EmGFP, green), resulting in TCC formation (red) and cell lysis (blue) following addition of active complement. B. No TCC formation was observed with the MOG-IgG positive serum when incubated with inactive complement, resulting in fewer DAPI stained cells (blue). Images are representative of similar staining patterns observed in independent complement activation assays of the 17 MOG-IgG positive patients (Table 3). Images are shown in 20 × (A-upper panel and B) and 63 × (A-lower panel) magnification.