Because IL-12 signaling in oligodendrocytes acts through STAT4/pSTAT4 (ref. 58), which can lead to an increase in interferon-γ known to generate myelin and oligodendrocyte loss in aged mice59, the co-occurrence and interplay of neuroinflammation and myelin defects may exacerbate AD pathology by creating a ‘vicious circle’. The gene discussed is STAT4; the disease is Alzheimer disease.