The Ro/SS-A antigen is comprised or an acidic 60kD protein that may also be associated with a RNA ranging in size from 80 to 112 bases. The antigenic activity of the Ro/SS-A antigen appears to be independent of the RNA since the precipitin activity remains after treatment with RNase or separation from the RNA. Anti-Ro/SS-A autoantibodies were described originally as precipitating autoantibodies in sera of Sjogren's Syndrome and Systemic Lupus Erythematosus patients.
The presence of autoantibodies against the Ro/SS-A antigen may be used as a diagnostic aid. Elevated levels of Anti-Ro/SS-A have been detected in as high as 96% of Sjogren's Syndrome patients, 49% of patients with Systemic Lupus Erythematosus, 83% of mothers of infants with isolated complete congenital heartblock or Neonatal Lupus Dermatitis, and over 75% of patients with Subacute Cutaneous Lupus. Recently, a strong correlation between low positive levels of Anti-Ro/SS-A and subdinical dry eyes or mouth was found in a substantial portion of an elderly population.
In addition, it has been shown that 70% of patients with Ro/SS-A precipitating antibodies also have rheumatoid factor. The titer of rheumatoid factor and the concentration of Anti-Ro/SS-A have been closely correlated in Primary Sjogren's Syndrome. Recent developments in ELISA methodology have increased the sensitivity and the ability of the diagnostician to quantitate patient antibody titers.
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