JO-1

Anti-Jo-1 antibody is a myositis-specific autoantibody most commonly found in patients with idiopathic inflammatory myopathies (IIM).

Presence of Jo-1 (antihistidyl transfer RNA [t-RNA] synthetase) antibody is associated with polymyositis and may also be seen in patients with dermatomyositis.

Myositis means inflammation of the muscles that you use to move your body. An injury, infection, or autoimmune disease can cause it. Two specific kinds are polymyositis and dermatomyositis.

Idiopathic inflammatory myopathy (IIM) is a group of disorders characterized by inflammation of the muscles used for movement (skeletal muscles). Idiopathic inflammatory myopathy usually appears in adults between ages 40 and 60 or in children between ages 5 and 15, though it can occur at any age.

Polymyositis (PM) is one of the inflammatory myopathies, a group of muscle diseases that involves inflammation of the muscles or associated tissues, such as the blood vessels that supply the muscles. A myopathy is a muscle disease, and inflammation is response to cell damage.

Dermatomyositis (DM) is characterized by a skin rash that precedes or accompanies progressive muscle weakness. The rash appears patchy, with purple or red discolorations, and characteristically develops on the eyelids and on muscles used to extend or straighten joints, including knuckles, elbows, knees, and toes.

Interstitial lung disease (ILD, IPF) is an umbrella term used for a large group of diseases that cause scarring (fibrosis) of the lungs. The scarring causes stiffness in the lungs which makes it difficult to breathe and get oxygen to the bloodstream. Lung damage from ILDs is often irreversible and gets worse over time.

This antibody is directed against the histidyl-tRNA synthetase which catalyses the binding of the histidine to its cognate tRNA during protein synthesis. It can be considered a specific marker of IIM, predominantly found in 20-30% of patients with Polymyositis (PM) and in the 60-70% of those with interstitial pulmonary fibrosis (IPF). These antibodies are also found in Dermatomyositis (DM), although less frequently than in Polymyositis (PM), and are rare in children with PM or DM and in other connective tissue diseases.

The detection of this antibody is particularly useful in diagnosis and classification of IIM. Moreover, anti-Jo-1 serum levels strongly correlate with disease activity representing a good marker for disease monitoring.

References:

Zampieri S, Ghirardello A, Iaccarino L, Tarricone E, Gambari PF, Doria A. Anti-Jo-1 antibodies. Autoimmunity. 2005 Feb;38(1):73-8. doi: 10.1080/08916930400022640. PMID: 15804708. [L]