Cold Spring Harbor Laboratory researchers reported a mechanistic link between cancer immune responses and autoimmune brain disease in Nature. Their findings focus on ectopic NMDAR expression in cancer and the downstream development of germline-encoded autoimmunity. Using a mouse model in which tumors express NMDA receptors, the team tracked antibodies associated with anti-NMDA receptor responses and showed that strong anti-NMDA receptor antibody activity aligned with the immune response to tumor development. Importantly, the same antibody infusion into brains without cancer produced symptoms consistent with anti-NMDA receptor encephalitis, including seizures. The work suggests antibody characterization could help separate protective antitumor immunity from harmful neurological autoimmunity, supporting future therapeutic strategies that preserve immune function while reducing brain inflammation risk.