The C4d labeling was specific for GFAP autoimmunity and was not detectable on astrocytes in GFAP-antibody-negative cases of anti-Ma2-associated encephalitis (n = 1), anti-neuronal autoimmune encephalitis (anti-NMDAR n = 3, anti-AMPAR encephalitis n = 2), Alzheimer’s disease (n = 2), MOG antibody associated disorders (n = 1), stroke (n = 1) and healthy controls (n = 6). This evidence concerns the gene PNMA2 and viral encephalitis.