Extractable Nuclear Antigens are soluble cytoplasmic and nuclear components that are antibody

Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

 targets with over 100 different antigen

Antigen

An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...

s described.

The main 6 used in immunological laboratories for detection are Ro, La, Sm, RNP, Scl-70 and Jo1, which are screened for by Ouchterlony double immuno diffusion

Ouchterlony Double Immuno Diffusion

Ouchterlony double immunodiffusion is a simple, rather dated method which is still considered to be the gold standard for detection of extractable nuclear antigens...

 techniques and confirmed by Immuno blotting. Antibodies to these antigens have particular associations with various connective tissue disorders.

On anti-nuclear antibody

Anti-nuclear antibody

Anti-nuclear antibodies are autoantibodies directed against contents of the cell nucleus....

 tests, they have a speckled pattern.

Terminology

ENAs originally referred to proteins found in a saline extract of cell nuclei. Its components have since been more clearly identified and in fact include many cytoplasmic molecules. The misnomer however has stuck. These proteins are intimately associated with various RNA molecules and are thus called ribonucleoproteins, but the nomenclature used for them is often a source of confusion, Sm, Ro and La were named after the first 2 letters of the surnames of the patients in whom they were first found. Two proteins associated with Sjogren's Syndrome were independently described as antigens A and B, but are now known to be identical to Ro and La respectively. i.e. SS-A = Ro and SS-B = La.

ENA 4

ENA 4 is a grouping of antibodies often used to screen for mixed connective tissue disease

Mixed connective tissue disease

In medicine, mixed connective tissue disease , commonly abbreviated as MCTD, is an autoimmune disease, in which the body's defense system attacks itself. It was characterized in 1972....

 (MCTD), Sjögren's syndrome

Sjögren's syndrome

Sjögren's syndrome , also known as "Mikulicz disease" and "Sicca syndrome", is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva....

 and systemic lupus erythematosus

Systemic lupus erythematosus

Systemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune disease that can affect any part of the body. As occurs in other autoimmune diseases, the immune system attacks the body's cells and tissue, resulting in inflammation and tissue damage...

and commonly is composed of four tests:

• anti-Sm (for SLE)
• anti-RNP (for MCTD)
• anti-La (for Sjögren's)
• anti-Ro (for Sjögren's)