Antibody to the La antigen is detected in approximately 15% of SLE patients. It is also detected in a higher percentage (60-70%) of the sera of patients with Primary Sjögrens syndrome. In both cases it is almost always associated with anti-Ro. Except for the overlapping presence of SS in patients with SLE, there do not appear to be any distinguishing clinical features which are associated with the presence of anti-La.Anti-La antibodies give a fine nuclear speckled pattern of staining on Hep2 cells. However this staining is often obscured by a homogeneous pattern due to other specificities of anti-nuclear antibody in the same sera. La antigen is associated with Ro in specific small ribonucleoprotein complexes. Although it is predominantly located in the nucleus the La protein has a role in transport of some RNAs into the cytoplasm. Autoantibodies recognise conformational and linear epitopes throughout the molecule.
Autoantibody associated with SLE or Sjögrens syndrome. Important in pregnancy where there is suspicion of congenital heart block.
Antibodies to La are found in 25-80% of patients with primary Sjögrens syndrome particularly those with hyper-gammaglobulinaemia, extra glandular manifestations, especially vasculitis and cytopaenias. 20-90% of patients with secondary Sjögrens have antibodies to La. It is uncommon for patients with Sjögrens syndrome not to have anti-La antibodies.The 5-15% of patients with SLE having anti-La antibodies usually are those with associated Sjögrens syndrome and seldom those with severe kidney involvement. The levels do not correlate with disease activity. 25-40% of Patients with subacute cutaneous lupus are Ro and La positive though Ro alone can also be characteristic.
Anti-La antibodies are found, usually together with anti-Ro antibodies in most mothers of babies with complete congenital heart block although a minority of babies born to mothers with La and autoimmune diseases will develop heart block.
Serum Separator Tube (SST)
Fluorescence enzyme linked immunoassay (Phadia Immunocap 250): Human recombinant La protein IgG antibodies.
Test is only carried out when ENA screen is positive.
Results reported as negative, equivocal or positive.
5 – 7 days
Immunology The James Cook University Hospital