SS-A/Ro(SSA) and SS-B/La(SSB) Antibodies
SS-A/Ro and SS-B/La are distinct small intracellular RNA-protein complexes. Antigenic reactivity resides in the protein components. Tests for antibodies to SS-A/Ro and SS-B/ La are useful in the diagnosis of SLE and Sjogren's Syndrome.
Antibodies to the ribonucleoprotein SS-A (Ro) are detected in 35 to 60% of SLE patients. Anti SS-A autoantibodies have been associated with photosensitivity, sicca symptoms, thrombocytopenia, and subacute cutaneous LE rash. Subacute cutaneous lupus erythematosis is a widespread, non-scarring, often photosensitive, form of cutaneous lupus with mild systemic manifestations and a low frequency of CNS and renal involvement. Anti SS-A (Ro) antibodies are strongly associated with neonatal lupus. Maternal IgG antibodies cross the placenta, causing disease in the neonate.The two major manifestations of neonatal lupus erythematosis are transient dermatitis and permanent heart block. Photosensitive dermatitis develops after the first few weeks of life and resolves within 6 months, coincident with the clearing of maternal antibodies from the infant’s circulation. Heart block is due to binding of SS-A antibodies in conducting system tissue.
Lymphocytic infiltration of exocrine glands, particularly the salivary and lacrimal glands, and other organs characterize Sjogren syndrome. The most common clinical presentation is with sicca symptoms, xerophthalmia and xerostomia. The autoantibodies most closely associated with Sjogren syndrome are directed against the ribonucleoproteins SS-A (Ro) and SS-B (La). SS-A antibodies are detected in 40 to 60% of patients with Sjogren syndrome. SS-B (La) antibodies occur slightly less frequently and never occur in the absence of SS-A antibodies. The presence of SS-A and SS-B antibodies can be used to support the diagnosis of Sjogren syndrome. However, their presence must be interpreted in the proper clinical context because they are also found in patients with SLE and other diseases. In addition to diagnosis, these antibodies provide some prognostic information. Patients with these antibodies more often have extraglandular disease including vasculitis, purpura, lymphadenopathy, leukopenia, thrombocytopenia, hypergammaglobulinemia, and the presence of rheumatoid factor.
Results are reported as positive or negative. Reference value is negative.
Specimen requirement is one SST tube of blood.
