Serum and CSF autoimmune encephalitis antibodies, including anti-NMDAR, anti-AMPAR1, anti-AMPAR2, anti-LGI1, anti-CASPR2, anti-GABABR, anti-DPPX, anti-igLON5, and anti-GAD65 were all negative by cell-based assay, with the exception of anti-mGluR5 being positive either in the cerebrospinal fluid (1:3.2) or serum (1:100) (Fig. 4), while tissue-based assay in monkey cerebellum was negative. Here, GRM5 is linked to autoimmune encephalitis.