Anti-SS-A (Ro)
IgG antibodies to SS-A (52 and 60 kDa) in blood serum are used for differential diagnosis and monitoring of autoimmune rheumatoid diseases (systemic lupus erythematosus, Sjogren's syndrome). Antibodies belong to the group of cytoplasmic antigens. Immunoreactive proteins can occur in various combinations and also bind to proteins of viral origin. A link has been noted between mixed connective tissue disease and viral infection with Epstein-Barr virus.
In patients with systemic lupus erythematosus (SLE) without anti-dsDNA, anti-ssDNA, anti-SS-A and anti-SS-B antibodies are very often detected. There was a strong correlation between the concentration of antibodies and the severity of the disease with an increase in the concentration of antibodies in the active stage. Antibodies of a certain type are not specific to only one disease, but can occur in various combinations. The peculiarities of finding different combinations of antibodies and their concentrations together with the general clinical picture of the patient are an important diagnostic tool in the assessment of rheumatoid autoimmune diseases. The SS-A and SS-52/60 proteins bind to small RNA and ribonucleoprotein particles in the cell nucleus and cytoplasm and is a component of the human cytoplasmic ribonucleoprotein complex. Autoantibodies against these two antigens are primarily found in collagenoses, in particular, Sjogren's syndrome and various forms of lupus erythematosus. Autoantibodies to SS-A and SS-B components are present in 40-80% of patients with primary Sjogren's syndrome and 30-50% of patients with SLE. In patients with Sjogren's syndrome, antibodies to SS-A and SS-B are often found in combination. Due to the strong association of SS-A and SS-B antibodies with HLA-DR3 and DR2 phenotypes, a genetic predisposition is assumed.
Sjogren's syndrome is a chronic autoimmune disease affecting the salivary and lacrimal glands, which leads to xerostomia and xerophthalmia. The detection of antibodies to SS-A and SS-B in a patient with Sjogren's syndrome can predict the development of such extraglandular manifestations of the disease as vasculitis, lymphadenopathy, splenomegaly, anemia and leukopenia. Antibodies to SS-A are usually found in the population of patients with SLE with pronounced symptoms of photosensitive skin manifestations. In SLE, accompanied by the appearance of antibodies to Ro/SS-A, glomerulonephritis is less common than in patients with a high titer of antibodies to dsDNA, but there is a certain risk of developing skin lesions and underlying risk for increased photosensitivity.
The determination of antibodies to SS-A component in women during pregnancy as a risk factor for the development of severe cardiac pathology in the fetus is of great importance. Antibodies to SS-A are found in 98% of mothers whose children suffer from neonatal lupus syndrome. The basis of this disease is the penetration of antibodies to SS-A into the blood of a newborn through the placenta. The main manifestation of congenital lupus is dermatomyositis and a number of systemic and hematological syndromes, including congenital transverse blockade, hepatitis, hemolytic anemia and thrombocytopenia. About half of mothers with children with congenital lupus are usually asymptomatic before the baby is born. After birth, most asymptotic mothers develop a picture of a connective tissue disease. All pregnant women with suspected mixed connective tissue disease should be immunologically examined to identify the risk group for congenital lupus in the fetus.