RTN4 and myeloid sarcoma: An immunohistochemical study by Satoh et al. confirmed Nogo-A overexpression in oligodendrocytes at the edge of chronic active demyelinating lesions in patients with MS, and unexpectedly marked immunoreactivity for NgR in reactive astrocytes and microglia/macrophages in these lesions in comparison with their expression in the white matter of brains of neurologically normal subjects.