Testing of antibodies against the ITPR1 antigen is indicated in the investigation of patients with suspected autoimmune encephalitis or autoimmune cerebral ataxia.
The presence of autoantibodies against the inositol 1,4,5-triphosphate receptor type 1 (ITPR1) has been reported in cases of autoimmune cerebral ataxia. Inositol 1,4,5-triphosphate receptors are located on intracellular membranes, such as the endoplasmic reticulum. Inositol 1,4,5-triphosphate receptors play an important role in intracellular calcium (Ca++) signaling in various cell types. The ITPR1 antigen is an intracellular antigen. Some data indicate that this autoantibody may be present in patients with non-small cell lung cancer.
The presence of ITPR1 autoantibodies should be considered in the differential diagnosis of patients with subacute cerebral ataxia of unknown etiology.
In general, immunotherapy treatment is more effective against autoantibodies directed against extracellular antigens than for autoantibodies against intracellular antigens.
See also: Anti-Neuronal Antibodies