(Ro) SSA Antigen

The (Ro) SS-A antigen is comprised or an acidic 60 kD protein that may also be associated with a RNA ranging in size from 80 to 112 bases (1). 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 (1).  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 (2), 49% of patients with Systemic Lupus Erythematosus (2), 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 (3).  In addition, it has been shown that 70% of patients with (Ro) SS-A precipitating antibodies also have rheumatoid factor (4). The titer of rheumatoid factor and the concentration of Anti-(Ro) SSA have been closely correlated in Primary Sjogren’s Syndrome (4).

1. Mamula MJ, Fox OF, Yamagata H, and Harley JB. “The (Ro) SS-A Autoantigen as an Immunogen Some Anti-(Ro) SSA Antibody Binds IgG.” J of Exp Med Vol 86: pg 1889-1901.
2. Rader MD, O’Brien C, Liu Y, Harley JB, and Reichlin M. “Heterogeneity of the (Ro) SSA Antigen, Different Molecular Forms in Lymphocytes and Red Blood Cells.” J. Clin. Invest Vol 83: 1989, pg 1293-1298.
3. Harley JB, Kaine JL, Fox OF, Reichlin M, Gruber B. “Ro SSA Antibody and Antigen in Cogenital Complete Heart Block ((Ro) SSA and Heart Block).” University of Oklahoma, Health Science Center, Arthritis and Immunology Program, Oklahoma Medical Research Foundation, pg 1-16.
4. Harley JB, Alexander EL, Bias WB, Fox OF, et al. “Anti-(Ro) SSA and Anti-(La) SSB in Sjogren’s Syndrome.” Dept of Med, University of Oklahoma, Health Science Center, Arthritis and Immunology Program, Oklahoma Medical Research Foundation, pg 1-35.