Molecular and serological diversity of anti-DNA autoantibodies from NZB and (NZB X NZW) F1 mice

Variable region cDNA sequences of three mouse monoclonal anti-idiotypic antibodies specific for anti-alpha(1----6)dextrans with groove- or cavity-type combining sites

The variables regions of three syngeneic anti-idiotypic antibodies (Ab2s) were cloned and sequenced. They are encoded by different VL genes, two are from different members of V kappa-Ox1 superfamily. The H chains are encoded by VH genes belonging to three different VH families, J558, Q52 and 7183. Together with a previous report from this laboratory, the nucleotide sequences of four Ab2s to anti-alpha(1----6)dextrans have been presented. They are derived from a number of unrelated germline genes, and differ from similar studies in anti-NP, anti-GAT and anti-Ars systems. Three of four Ab2s in the anti-alpha(1----6)dextran system appear to have D-D fusions, which has also been reported in several other Ab2s.

Correlation between the occurrence of lupus nephritis, anti-erythrocyte autoantibodies and V kappa haplotype in NZB x 129/J and NZB x SM/J recombinant inbred murine strains

The NZB mouse is genetically predisposed to the development of autoimmune disease that resembles the human autoimmune systemic lupus erythematosus and autoimmune hemolytic anemia, with increased titers of anti-DNA, and Coombs' autoantibodies. The various autoimmune traits are controlled separately by a limited number of genes. Genetic studies have shown that several immune loci are involved in autoimmunity: T cell abnormalities, H-2 complex and immunoglobulin genes have been implicated. In this report, we present evidence for a significant correlation of NZB V kappa 1 haplotype defined by restriction fragment length polymorphism analysis with anti-erythrocyte autoantibodies in NZB x 129/J and NZB x SM/J recombinant inbred lines.

Ionic binding characteristics of monoclonal autoantibodies to DNA from NZB.H-2bm12 mice

NZB (H-2d) mice are well known for the production of IgM autoantibodies to ssDNA. However, an F1 cross between NZB and either NZW or SWR mice is required to produce IgG nephritogenic antibodies to dsDNA and glomerulonephritis. The contribution of parental class II loci in the hybrid mice is clearly important to the development of anti-dsDNA antibodies. In contrast, NZB mice congenic with the Iabm12 mutation develop IgG autoantibodies to dsDNA despite being homozygous for Ia. As a part of our effort to examine the mechanisms of disease development in NZB.H-2bm12 mice, we have generated a panel of monoclonal antibodies against nucleic acids. A subgroup of these antibodies exhibited strong electrostatic interaction with nucleic acids as evidenced by inhibition of their binding by a moderate increase in ionic strength. Interestingly, the effect of salt was either all or none; e.g., antibodies were either markedly inhibited or virtually unaffected. The importance of this ionic interaction was highlighted by analysis of DNA binding of antibodies from serum and nephritic kidneys of NZB.H-2bm12 mice. Antibodies specific for ssDNA, which are common in NZB mice and not associated with nephritic lupus, are largely unaffected by salt. However, serum and kidney eluted IgG antibodies specific for dsDNA were markedly inhibited by salt. We postulate that B cell clones whose antibodies exhibit electrostatic interaction with DNA are preferentially expanded during the course of lupus in NZB.H-2bm12 mice and that such antibodies contribute significantly to glomerulonephritis.

Structural characteristics of the variable regions of immunoglobulin genes encoding a pathogenic autoantibody in murine lupus

We have studied several monoclonal anti-double-stranded (ds) DNA antibodies for their ability to accelerate lupus nephritis in young NZB X NZW F1 female mice and to induce it in BALB/c mice. Two identified as pathogens in both strains have characteristics previously associated with nephritogenicity: expression of IgG2a isotype and IdGN2 idiotype. Both pathogenic antibodies used the combination of genes from the VHJ558 and VK9 subfamilies. Two weak pathogens failed to accelerate nephritis in young BW mice, but induced lupus nephritis in BALB/c mice. They both express IdGN2; one is cationic and an IgG3, the other is an IgG2a. Additional MAbs (some IgG2a, one IdGN2-positive) did not accelerate or induce nephritis. We have cloned and sequenced the variable regions of the immunoglobulin genes of one pathogenic autoantibody. No unique V, D, or J gene segments and no evidence of unusual mechanisms in generating diversity were used to construct this antibody. These data argue against use of unique abnormal Ig genes by systemic lupus erythematosus individuals to construct pathogenic autoantibody subsets. Instead, the major abnormality may be immunoregulatory.