In a multicenter study more than 300 central European systemic lupus erythematosus (SLE) patients were examined for HLA-B, HLA-DR, and complement C4 phenotypes. For 174 SLE patients MHC haplotypes were determined by family segregation analysis, and for 155 patients C4 gene deletions were determined by TaqI restriction fragment length polymorphism. Two haplotypes, B8-C4AQO-C4B1-DR3 and B7-C4A3-C4B1-DR2, were identified as risk factors for SLE. These findings were confirmed by applying the haplotype frequency difference (HFD) method, which uses nontransmitted haplotypes from the family study as internal controls. Furthermore, only HLA-DR2, but not DR3, B7, or B8, was significantly increased in SLE patients independently of the two risk haplotypes. C4A gene deletions, but not silent C4AQO alleles, were increased in SLE patients and neither C4BQO alleles nor C4B gene deletions were increased. The observed frequencies of homozygosity and heterozygosity for the two haplotypes and the frequencies of homozygotes for C4AQO and C4A deletions did not differ from the expected values, indicating that the risk for SLE is conveyed by single allele effects. In conclusion, there are two MHC-linked susceptibility factors for Caucasian SLE patients carried by the haplotypes B7-DR2 and B8-DR3. The results argue against C4QO alleles being the decisive factors increasing susceptibility to SLE. (J. Clin. Invest. 1992Invest. . 90:1346Invest. -1351

Antibodies against dsDNA of the IgM class were measured in sera of 352 patients with systemic lupus erythematosus, 81 blood donors and 189 patients with rheumatoid arthritis using a new ELISA based on human recombinant dsDNA as antigen. IgM anti-dsDNA antibodies were found in 52.3% of the sera from patients with systemic lupus erythematosus, but in none of the sera from 81 normal controls and 189 patients with rheumatoid arthritis. The association of these autoantibodies with 31 clinical and 37 laboratory parameters was calculated. There was a highly significant negative correlation between IgM anti-dsDNA antibodies and nephritis as well as all the laboratory parameters indicating renal disease (elevated serum creatinine concentration, proteinuria, erythrocyte casts in the urine). IgM anti-dsDNA antibodies indicate protection of lupus patients against the development of lupus nephritis. Further experiments will show whether application of IgM anti-dsDNA antibodies is effective in treating lupus nephritis.

The prevalence and clinical and laboratory associations of IgM, IgG and IgA rheumatoid factors (RF) were determined in 352 patients with systemic lupus erythematosus (SLE). IgM, IgG, and IgA class RF were detected in 17.9%, 20.5%, and 20.5% of the sera, respectively. RF were associated with sicca syndrome, hypergammaglobulinemia, high titer of antinuclear antibodies, anemia, SSA- and SSB-antibodies, and with the presence of HLA-DR3. RF correlated negatively with nephritis and livedo racemosa. Moreover, we observed an association of RF and parameters of inflammatory activity such as elevated erythrocyte sedimentation rate (ESR) and leukopenia. Analysis of immunoglobulin classes revealed that laboratory parameters of inflammatory activity, SSA- and SSB-antibodies and HLA-DR3 correlated with IgA RF only. IgA RF define a subgroup of SLE patients characterized by distinct autoimmune phenomena and high disease activity in the absence of nephritis.

Previously it has been suggested that the presence of antibodies against dsDNA of the IgA class may define a subset of systemic lupus erythematosus (SLE) patients suffering from nephritis and arthritis. Therefore, these autoantibodies were measured in sera of 352 patients with SLE, 81 blood donors, and 189 patients with rheumatoid arthritis using a new ELISA based on human recombinant dsDNA as antigen. IgA anti-dsDNA antibodies were found in 19.9% of the sera from patients with SLE, but in none of the sera from 81 normal controls and 189 patients with rheumatoid arthritis. The association of these autoantibodies with 31 clinical and 36 laboratory parameters was calculated. IgA anti-dsDNA antibodies were found to be associated with parameters of disease activity such as elevated erythrocyte sedimentation rate and consumption of complement component C3, and the clinical parameters vasculitis, with necrosis and erythema, but not with nephritis and arthritis. Therefore, IgA anti-dsDNA antibodies define a subset of SLE patients, and monitoring of IgA anti-dsDNA antibodies may be helpful as a prognostic parameter in patients with SLE.