NEUROIMMUNOLOGY

Aquaporin-4 Autoantibody (AQP4Ab) ELISA

ELISA test kit for the measurement of autoantibodies to aquaporin-4 (AQP4Ab). Aquaporin-4 is the most abundant water channel protein in the central nervous system and is expressed extensively within the brain and spinal cord regions.

Voltage-Gated Calcium Channel Antibody (VGCCAb) RIA

RIA test kit for the measurement of autoantibodies to the voltage-gated calcium channel (VGCC). The release of acetylcholine is regulated by the influx of calcium through voltage-gated channels (VGCC) in nerve terminals. Antibodies directed against these calcium channels are thought to reduce calcium influx and inhibit acetylcholine. To date, several subtypes of calcium channels have been described based upon their biophysical and pharmacological properties.

Lambert-Eaton Myasthenic Syndrome

MYASTHENIA GRAVIS

Acetylcholine Receptor & Acetylcholine Receptor Autoantibodies (AChRAb)

Human muscle acetylcholine receptors (AChR) exist as two developmentally regulated subtypes:

Fetal AChR


Adult AChR


The fetal AChR is pentameric with stoichiometry of 2a : b : g : d. In the adult subtype, expression of the e subunit is induced and replaces the g subunit within the AChR pentamer.

Autoantibodies to the Acetylcholine receptor (AChRAb) can be detected in 80-90% of patients with myasthenia gravis. Myasthenia gravis (MG) is a neuromuscular disorder which results from a disruption of normal nerve-to-muscle signal transmission. The immunopathologic mechanisms by which normal signal transmission is disrupted are thought to be:

1. blocking of the receptor as a result of the direct binding of the autoantibody,
2. disruption of ACh binding to the receptor due to steric hindrance caused by autoantibody binding at sites adjacent to the ACh binding site,
3. destruction of the muscle membrane as a result of complement activation by autoantibodies,
4. increased receptor turnover due to autoantibody-receptor cross-linking.

Myasthenia Gravis

5. Conventional diagnostic assays for myasthenia gravis (MG) are derived from a source of AChR (either human muscle or the TE671 cell line) which is rich in the fetal subtype. While the majority of the anti-AChR autoantibodies in the sera of patients with MG recognize the fetal form of the AChR, some MG patient sera contain autantibodies that specifically bind to adult AChR.

Therefore, to increase the sensitivity of the acetylcholine receptor antibody (AChRAb) assay, the KRONUS acetylcholine receptor preparation has been adapted to include both fetal and adult AChR subtypes.