Screening for antibodies against the GABA B receptor is used in the case of suspected paraneoplastic syndromes especially in classical autoimmune encephalitis.
There are relatively few published cases, 50% of which were women, with ages ranging from 24 to 75 years (mean 62 years). Antibodies have been associated with small-cell lung cancer in 50-60% of cases. Antibodies can occur along with other autoantibodies in almost half of cases (antibodies against GAD-65, VGCC, and TPO antigens).
GABA B receptors belong to the group of extracellular antigens. The GABA B receptor is a metabotropic receptor for gamma-aminobutyric acid (GABA). Receptors of this type are found in the central nervous system and in the autonomic peripheral nervous system. In general, immunotherapy is often more effective in autoantibodies directed against extracellular antigens than in autoantibodies against intracellular antigens. The antibody titer against the GABA B receptor can be used to monitor the efficacy of treatment.