Methods of detecting and quantifying autoantibodies against neuronal antigens

A method of identifying and treating a subject having autoimmune encephalitis (AE) comprising:

• (1) detecting an autoantibody against a neuronal antigen in a biological sample obtained from the subject by:
• (a) transfecting a host cell with a plasmid comprising a nucleic acid encoding the neuronal antigen to produce a transfected host cell having the neuronal antigen expressed thereon;
• (b) mixing the transfected host cell of step (a) and a control host cell having a first fluorophore labeled thereon to produce a mixture, in which the control host cell does not have the neuronal antigen thereon expressed thereon;
• (c) adding the biological sample to the mixture of step (b), in which the biological sample has been diluted at least 15 times before adding to the mixture of step (b);
• (d) adding an anti-human antibody to the product of step (c), wherein the anti-human antibody is conjugated to a second fluorophore.
• (e) irradiating the products of step (d) independently with a first light having a first wavelength to excite the first fluorophore and a second light having a second wavelength to excite the second fluorophore;
• (f) measuring respective signals emitted from the excited first and second fluorophores at a third and fourth wavelengths;
• and
• (g) subtracting the signal measured at the third wavelength from the signal measured at the fourth wavelength thereby producing a real signal, which indicates the presence of the autoantibody in the biological sample;
• wherein, steps (b) and (c) are conducted in the same vessel;
• and
• (2) treating the subject by administering solumedrol or immunoglobulin (Ig) to the subject to ameliorate symptoms associated with AE.