GAD65Ab

GAD65Ab refers to antibodies against glutamic acid decarboxylase 65 kDa isoform. Glutamic acid decarboxylase (GAD) is an enzyme responsible for synthesizing gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system. GAD exists in two main isoforms, GAD65 and GAD67. GAD65Ab specifically targets the GAD65 isoform.

The presence of GAD65Ab is primarily associated with autoimmune neurological disorders. It is a well-established biomarker for stiff-person syndrome (SPS), a rare neurological condition characterized by progressive muscle stiffness and spasms. In SPS, GAD65Ab are thought to contribute to the disease by interfering with GABAergic neurotransmission, leading to disinhibition and heightened motor neuron excitability.

GAD65Ab can also be found in other autoimmune conditions, including type 1 diabetes, limbic encephalitis, and cerebellar ataxia, often in conjunction with other autoantibodies. The detection of GAD65Ab is typically performed using enzyme-linked immunosorbent assays (ELISAs) or indirect immunofluorescence assays on serum samples. Elevated levels of GAD65Ab can aid in the diagnosis and classification of certain neurological disorders, guiding treatment strategies, which may include immunosuppressive therapies. While the presence of GAD65Ab indicates an autoimmune process, its precise pathogenic role and correlation with disease severity can vary among individuals and different conditions.