Immunoglobulin Class and Subclass Profile of the Ro/SS-A Autoantibody Response

• Published in: Journal of investigative dermatology Vol. 90; no. 2; pp. 158 - 164
• Main Authors: Lieu, Tsu-San, Reimer, Charles B., Sontheimer, Richard D.
• Format: Journal Article
• Language: English
• Published: Danvers, MA Elsevier Inc 01.02.1988; Nature Publishing
• Subjects: Animals; Autoantibodies; Autoantibodies - analysis; Autoantibodies - classification; Autoantigens - immunology; Biological and medical sciences; Coatings; Cutaneous Lupus Erythematosus; Cytotoxicity; Dermatology; Enzyme-Linked Immunosorbent Assay; Humans; Hydrogen-Ion Concentration; Immunodiffusion; Immunoglobulin A; Immunoglobulin G; Immunoglobulin G - analysis; Immunoglobulin G - classification; Immunoglobulin M; Immunoglobulin M - analysis; Immunoglobulin M - classification; Immunosuppressive Agents - pharmacology; Latex; Lupus Erythematosus, Cutaneous - immunology; Lymphocytes T; Medical sciences; Mice; Monoclonal antibodies; pH effects; Prednisone; Rheumatoid factor; Rheumatoid Factor - analysis; Ribonucleoproteins; RNA, Small Cytoplasmic; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; Human; Connective tissue disease; Chronic; Immunoglobulins; Skin disease; Immunological investigation; Antigen RO-SSA; Lupus erythematosus; Disseminated; Subacute
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1111/1523-1747.ep12462142

We have developed an enzyme-linked immunosorbent assay (ELISA) for autoantibody to Ro/SS-A antigen (anti-Ro/SS-A) in order to more fully characterize the autoimmune response that occurs to this antigen in patients with subacute cutaneous lupus erythematosus (SCLE). The microtiter plate – immobilized, biochemically purified Ro/SS-A antigen reacted with anti-Ro/SS-A antibody, but not with other closely related specificities (anti-La/SS-B, anti-SM, anti-U1-RNP) or normal sera. The optimal pH of antigen – antibody reaction in this ELISA was 7.2. The binding of sera containing anti-Ro/SS-A was inhibited 80% by preincubation with the same amount of Ro/SS-A antigen used for coating the plate. Although 11 of the 14 (79%) SCLE sera studied had precipitating anti-Ro/SS-A antibody by immunodiffusion, 13 (93%) sera had abnormally elevated IgG, IgA, or IgM ELISA binding levels. A good correlation between IgG anti-Ro/SS-A ELISA binding levels and immunodiffusion titers was observed (r – 0.8588, p ≤ 0.001) suggesting that IgG is the major anti-Ro/SS-A antibody class detected by double immunodiffusion, Sera with a combination of high rheumatoid factor levels (latex 3+ or higher) and high anti-Ro/SS-A titers (1 : 8 or higher in immunodiffusion) tended to give an abnormally high IgM anti-Ro/SS-A ELISA binding levels. After rheumatoid factor activity was removed by absorption with heat-aggregated human IgG, a 50% decrease in IgM anti-Ro/SS-A ELISA binding was noted. On the other hand, absorption of rheumatoid factor – negative sera that contained high IgM anti-Ro/SS-A binding activity did not significantly decrease ELISA binding levels. Prednisone and 6-azathioprine reduced the level of IgG anti-Ro/SS-A autoantibody in sera of treated SCLE patients by 50%. The IgG subclass profile of anti-Ro/SS-A autoantibody was analyzed by using mouse monoclonal antibodies specific for the 4 human IgG subclasses. Of anti-Ro / SS-A positivie SCLE sera, 91% had predominatly IgG1 subclass autoantibody. The coexistence of IgM and IgG anti-Ro/SS-A autoantibody and the predominance of the IgG1 subclass is compatible with the possibility that this autoantibody response is under T-cell control. The predominance of IgG1 in the autoimmune response to Ro/SS-A antigen in SCLE patients is consistent with the hypothesis that antibody dependent cell mediated cytotoxicity could be an important immunologic effector mechanism in this disorder.