Samples were screened by immunohistochemistry performed on non-perfused rat or mouse brain, fixed by immersion with 4 % paraformaldehyde for 1 h and processed as reported [11 (link), 14 (link)]. Immunohistochemistry using a standard avidin–biotin peroxidase method was applied using patients' serum (diluted 1:200) or a commercial rabbit polyclonal anti-MOG antibody (Abcam; ab32760; diluted 1:2000) followed by biotinylated secondary antibodies, goat anti-human IgG (H + L) (Vector Laboratories, Burlingame, CA, USA) and goat anti-rabbit IgG (H + L) (Vector Laboratories, Burlingame, CA, USA) (diluted 1:1000), respectively. To show if hMOG-IgG of different patients with a common myelin staining pattern recognized similar epitopes, rat brain sections were pre-incubated with undiluted hMOG-IgG-positive serum for 3 h followed by biotinylated IgG obtained from the two patients described above and processed as reported [15 (link)].