Autoimmunity

Myasthenia gravis

Myasthenia gravis (MG) is caused by the failure of neuromuscular signal transmission. To confirm the diagnosis of MG the determination of acetylcholine receptors (ARAb) and muscle-specific receptor tyrosine kinase (MuSK) autoantibodies is needed.

The ARAb Radioimmunoassay can be used as a method for the measurement of autoantibodies in serum of 80-90 % of patients with generalized myasthenia gravis and in 55-70 % of patients with ocular myasthenia. In 10-20 % of the patients with generalized MG, and in up to 50 % of the patients with ocular MG these autoantibodies cannot be detected. In these cases the disease is commonly referred to as seronegative MG (SNMG). The antibodies to the muscle-specific receptor tyrosine kinase can be detected and measured via MuSK-Ab ELISA.

Agrin-induced clustering of acetylcholine receptors via MuSK

~ 50 % of all seronegative MG patients is MuSK positive

Coeliac disease

The immune-mediated inflammatory process following ingestion of wheat, rye, or barley proteins occurs in genetically susceptible individuals. Coeliac disease is associated with a variety of autoantibodies, including tissue transglutaminase (tTG) and gliadin antibodies.

Although the IgA isotype of these antibodies usually predominates in coeliac disease, individuals may also produce IgG isotypes. The most sensitive and specific serologic test is the tTG-IgA test.