Anti-Proteinase 3 antibodies (PR3-ANCA) are key in diagnosing Granulomatosis with Polyangiitis (GPA), an autoimmune disease where the immune system attacks blood vessels, mainly affecting the respiratory system and kidneys. Proteinase 3, an enzyme in neutrophils, is targeted by these antibodies, leading to vessel inflammation and damage. High levels of anti-PR3 antibodies indicate active GPA, aiding in its management and treatment decisions. This understanding is vital for developing targeted therapies to control the disease.

Acetylcholine receptors are responsible for binding acetylcholine, a neurotransmitter for signal transduction in CNS. They are localized in neuromuscular junctions. Antibodies against acetylcholine receptor are found in myasthenia gravis disease, which destroys the receptor function, leading to a neuromuscular transmission defect, which then causes hypofunction, fatigue, and inflammation of skeletal muscles and produces serum antibodies against muscle antigens.

Acetylcholine receptors are responsible for binding acetylcholine, a neurotransmitter for signal transduction in CNS. They are localized in neuromuscular junctions. Antibodies against acetylcholine receptor are found in myasthenia gravis disease, which destroys the receptor function, leading to a neuromuscular transmission defect, which then causes hypofunction, fatigue, and inflammation of skeletal muscles and produces serum antibodies against muscle antigens.

Actin is responsible for regulating paracellular flow across the intestinal epithelium. However, increased levels of actin suggest epithelial cell damage leading to increased intestinal permeability and decreased barrier function.

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) is a compound that is a specific agonist for the AMPA receptor, where it mimics the effects of the neurotransmitter glutamate. In some epilepsies, antibodies to AMPA receptors leads to neuron damage. The same is true for ischemia, where oxygen deprivation leads to excitotoxicity. Conversely, Alzheimer's disease is characterized by decreased AMPA activation and synapse loss.

Antibodies against Amphiphysin occur in patients with paraneoplastic variant Stiff person syndrome but can also be seen in autoimmune encephalitis. Antibodies against Amphiphysin are associated with breast cancer and small cell lung cancer. Neurological symptoms may precede the diagnosis of cancer with up to five years. 

Antibodies against Amphiphysin are graded as High-risk antibodies with a frequency of 80% of underlying cancer and a positive result yield 3 points PNS score, according to Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. 

Antibodies against Amphiphysin occur in patients with paraneoplastic variant Stiff person syndrome but can also be seen in autoimmune encephalitis. Antibodies against Amphiphysin are associated with breast cancer and small cell lung cancer. Neurological symptoms may precede the diagnosis of cancer with up to five years. 

Antibodies against Amphiphysin are graded as High-risk antibodies with a frequency of 80% of underlying cancer and a positive result yield 3 points PNS score, according to Updated Diagnostic Criteria for Paraneoplastic Neurologic Syndromes. 

Antibodies to aquaporin 4 constitute a sensitive and highly specific serum marker of neuromyelitis optica (NMO) that can facilitate the differential diagnosis of NMO and classic multiple sclerosis.

Neuromyelitis optica is an inflammatory demyelinating disorder of the central nervous system (CNS). The discovery of circulating IgG antibodies against the astrocyte water channel protein aquaporin 4 (AQP4) and the evidence that AQP4 IgG is involved in the development of neuromyelitis optica revolutionized the understanding of the disease. Anti aquaporin 4 antibodies have also been shown in patients with peripheral demyelination. In addition, human aquaporin 4 shows cross-reactivity with corn and soybean aquaporins.

Antibodies to aquaporin 4 constitute a sensitive and highly specific serum marker of neuromyelitis optica (NMO) that can facilitate the differential diagnosis of NMO and classic multiple sclerosis.

Neuromyelitis optica is an inflammatory demyelinating disorder of the central nervous system (CNS). The discovery of circulating IgG antibodies against the astrocyte water channel protein aquaporin 4 (AQP4) and the evidence that AQP4 IgG is involved in the development of neuromyelitis optica revolutionized the understanding of the disease. Anti aquaporin 4 antibodies have also been shown in patients with peripheral demyelination. In addition, human aquaporin 4 shows cross-reactivity with corn and soybean aquaporins.

Anti-Beta2 Glycoprotein I IgG is a specific class of autoantibodies directed against beta-2 glycoprotein I (β2GPI), a plasma protein that plays a critical role in the regulation of coagulation. The presence of these autoantibodies is clinically significant, particularly in autoimmune disorders such as Antiphospholipid Syndrome (APS), where they contribute to a hypercoagulable state. APS, characterized by thrombosis and pregnancy morbidity, is often associated with the presence of anti-β2GPI IgG, along with other antiphospholipid antibodies like lupus anticoagulant and anti-cardiolipin antibodies.