Identification of a clinical subset of systemic lupus erythematosus by antibodies to the sm antigen

Abstract

Circulating antibodies to certain nuclear antigens are of diagnostic use and contribute to our ability to determine prognosis in terms of predicting particular organ system involvement in the rheumatic diseases. Examples include antibodies to DNA and to the Sm antigen associated with systemic lupus erythematosus (SLE) (l), antibodies to nuclear ribonucleoprotein n-RNP associated with mixed connective tissue disease (2), and antibodies to another nucleic acidic protein antigen, PM-1, which have a high specificity for polymyositis (3). A recent report of 16 patients who had circulating Sm antibodies suggested that this serologic pattern might be indicative of a more benign form of SLE with nonprogressive nephritis (4). The purpose of the present study was to compare the disease patterns in patients with circulating Sm and DNA antibodies and to determine the relative importance of the presence of Sm antibody or the absence of DNA antibody in the disease which occurred. MATERIALS AND METHODSCalf thymus nuclear extract, extractable nuclear antigen (ENA), and DNA were prepared by previously published techniques (5). The Sm antigen was prepared from the washed DNA-histone fraction of the nuclear extract. The resulting pellet was treated with DNase (Worthington Biochemical Corporation) for one hour at 37OC in the presence of 5 M/ml of MgCI,. The resulting supernatant, which had Sm antigen activity but no RNP activity, was further concentrated by 30% saturated ammonium sulfate, lyophilized, and stored at -10°C. This partially purified Sm antigen was then used in hemagglutination to determine the Sm antibody titer.All sera were analyzed for the presence of Sm and n-RNP by passive hemagglutination (2), immunodiffusion (6), and counterimmunoelectrophoresis (7) according to pre-

Antibodies to sm in patients with systemic lupus erythematosus. correlation of sm antibody titers with disease activity and other laboratory parameters

“…Our observation that SLE patients with antibodies to Sm have disease as severe as patients without antibodies to Sm is validated by the results of one group (24) and at variance with the results of another (25). In our study, 30 patients were followed over a 2.5-year period, and in each patient multiple sera were tested for antibodies to Sm and dsDNA.…”

“…In our study, 30 patients were followed over a 2.5-year period, and in each patient multiple sera were tested for antibodies to Sm and dsDNA. In the study by Winn et al (25), the disease was categorized in 135 different patients based on a single serum sample determination. We believe the conclusions drawn from this study (25) are incorrect based on 1) inadequate sequential blood samples obtained from individual patients and 2) the probable lack of specificity of the hemagglutination assay as employed for measuring antibodies to Sm.…”

The Autoimmune Antigen me is Distinct and Related to Undifferentiated Connective Tissue Disease

“…In particular, the correlations between Sm antibody and nephritis and/or central nervous system involvement have varied considerably in published studies (13)(14)(15)17). Because of the possible relationship between the Me and Sm antigens (although they have been shown to be immunologically distinct in this study) and the preliminary indications that the Me system is most frequently associated with a mild undifferentiated connective tissue disease, it is possible that the discordant results…”

“…While there is general agreement that Sm antibodies have a strong correlation with SLE (12), whether the presence of Sm antibodies is associated with mild or more severe clinical features has remained controversial (13)(14)(15)(16)(17). In particular, the correlations between Sm antibody and nephritis and/or central nervous system involvement have varied considerably in published studies (13)(14)(15)17).…”

“…While there is general agreement that Sm antibodies are found almost exclusively in sera of patients with SLE (12), attempts to define clinical subsets of patients with SLE by the presence or absence of these antibodies have led to conflicting reports (13)(14)(15)(16)(17) antigens. CTNE was prepared from fresh calf thymus tissue by modification (5,6,31) of a previously described method (2).…”