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AMPA Receptor Antibody

Alpha-Amino-3-Hydroxyl-5-Methyl-4-Isoxazolepropionic acid (AMPA) receptors are glutamate receptors that mediate fast excitatory neurotransmission in the brain. Antibodies targeting the extracellular domains of either or both GluR1 or GluR2 subunits have been associated with limbic encephalitis. Patients usually present with seizures, memory loss, mood changes, personality changes, psychosis, delirium or sleep disorders. A history of autoimmune disorders, cancer, or cancer risk factors increase the likelihood of autoimmune etiology.

Antibody can be detected in both serum and CSF. If antibody is detected in serum, subsequent testing of CSF adds little value. However, patients with negative serum results sometimes have positive CSF results. High titer antibodies are more specific for limbic encephalitis.

AMPA receptor antibody is detected using immunofluoresence to detect IgG binding to human cells transfected with GluR1 and GluR2 receptor subunits. Transfected cells over-express the cognate protein, increasing the sensitivity of the test. Specimen requirements are a red top tube of blood for serum antibody and 1 mL of CSF in a sterile vial for CSF antibody.

Reference value is no antibody detected.

Patients with limbic enephalitis due to AMPA receptor antibody may also have other coexisting autoantibodies such as anti-CRMP5, anti-GAD65 and anti-AGNA/SOX1.

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