Anti-Jo1 is an anti-nuclear antibody.

Anti-Jo1 has been associated with inflammatory myopathies such as polymyositis, dermatomyositis and antisynthetase syndrome.

It has histidine-tRNA ligase as a target.

Alternative name-Anti-tRNA Synthetase

The Jo1 system is an important marker antibody for this disease. 

Other aminoacid tRNA synthetases are also recognised by other polymyositis associated autoantibodies. 

Aminoacid tRNA synthetases autoantibodies give diffuse granular cytoplasmic staining on Hep-2 cells. 

Autoantibodies recognizing antigens known as Mi-1, Mi-2, Ki and Ku are also associated with polymyositis or polymyositis-scleroderma overlap.

Jo1 is primarily a cytoplasmic antigen. 

Anti-Jo1 is detected in the extractable nuclear antigen (ENA) screen. 

It is found in 25% cases of polymyositis and correlates with presence of pulmonary fibrosis. 

Jo1 is one of a number of related autoantigens associated with polymyositis.

The Jo1 antigen, histidyl tRNA synthetase is a cytoplasmic enzyme which incorporates histidine into growing polypeptide chains. 

Suspected polymyositis, dermatomyositis is an indication of testing for anti-Jo antibodies.

Antibodies to Jo1 are found in 20-60% patients with primary polymyositis or dermatomyositis and less commonly in association with other connective tissue disease. 

Anti-Jo1 positive patients tend to have the poorest prognosis with more prominent lung involvement and less skin involvement. 

Anti-Jo1 is often found along with other extractable nuclear antigens, particularly anti-Ro52

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