Comparison of the frequencies of arginines in heavy chain CDR3 of antibodies expressed in the primary B-cell repertoires of autoimmune-prone and normal mice.

Because the pathogenesis of anti-DNA Ab in SLE is correlated to Ab specificity for native DNA (dsDNA), understanding how such specificity is generated is important. The VH structures of most autoimmune anti-DNA antibodies include at least one arginine in VH-CDR3; moreover, antibody specificity for dsDNA can be correlated to the relative position of arginines in VH-CDR3. The coding sequences for most VH-CDR3 arginines among the anti-DNA MoAbs we have studied to date appeared to have been encoded by sequences generated during V-D-J recombination and would have been expressed in the primary B-cell repertoire. The frequency at which arginine codons are generated during V-D-J recombination therefore could potentially influence the frequency at which DNA-specific B cells are generated in the primary B-cell repertoire. The present study was undertaken to determine whether a higher percentage of B cells in the primary, preautoimmune repertoire of autoimmune-prone (NZB x NZW)F1 mice have immunoglobulin heavy chains with at least one VH-CDR3 arginine compared to B cells in the primary, preimmune repertoire of non-autoimmune-prone BALB/c mice. The present results indicate that mature B cells in preautoimmune (NZB x NZW)F1 mice, whether specific for DNA or not, are no more likely to have heavy chains with VH-CDR3 arginines than are B cells in BALB/c mice. The high frequency of recurrence of VH-CDR3 arginines among autoimmune anti-DNA in (NZB x NZW)F1 mice would appear to derive from the selective oligoclonal expansion of selected B cells that express such structures.

Monoclonal anti-DNA antibodies: structure, specificity, and biology.

Anti-DNA antibodies are a major contributor to the pathogenesis associated with the autoimmune disease systemic lupus erythematosus in mice and human. The accumulation of a large body of structural information on autoimmune anti-DNA antibodies over the past several years, particularly from mice, has provided considerable insight into the structure, function, and biology of this important class of autoantibodies. Even though the germline repertoire of light and heavy chain variable regions that may encode DNA-specific antibodies is very large in mice, there are individual light and heavy chain variable region genes that have been recurrent and preferentially expressed among anti-DNA hybridomas. This has been particularly true for hybridomas producing antibodies that bind duplex, B-form, mammalian DNA (dsDNA). Recurrent somatically derived variable region structures, particularly arginines in the third complementary-determining region of the heavy chain (VH-CDR3), have also been recurrent and preferentially expressed among monoclonal anti-DNA antibodies. In fact specificity for dsDNA can be correlated to the relative amino acid position at which arginines are expressed within VH-CDR3 of anti-DNA. Most important from the results of structural analyses of monoclonal anti-DNA autoantibodies has been the realization that autoimmunity to DNA results from a clonally selective, antigen-specific immune response to DNA. Autoimmune antibodies to DNA have all of the characteristics of secondary immune antibodies. In further support of this hypothesis, we have been able to induce anti-DNA antibodies in normal, nonautoimmune mice by immunization with immunogenic DNA-peptide complexes. The induced antibodies have all of the structural and functional characteristics of autoimmune anti-DNA including the pathogenetic potential to induce glomerulonephritis. This review summarizes the results of research from our laboratory that support the above conclusions.

Correlation between the amino acid position of arginine in VH-CDR3 and specificity for native DNA among autoimmune antibodies.

Autoimmunity to DNA in mouse models for the systemic autoimmune disease systemic lupus erythematosus (SLE) has all of the characteristics of an Ag-driven secondary immune response to DNA. Since the pathogenesis of anti-DNA Ab in SLE is correlated to Ab specificity for native DNA (dsDNA), understanding how such specificity is generated is important. As with immune A responses to most Ags, autoimmune Ab responses to DNA are dependent upon the clonal selection of B cells expressing particular H and L chain V-region structures. The VH structures of most autoimmune anti-DNA Abs include at least one arginine in VH-CDR3; moreover, previous results led us to propose that anti-DNA Ab specificity for dsDNA may be dependent upon the relative position of arginines in VH-CDR3. The present results demonstrate a strong correlation between specificity for dsDNA and arginine position in VH-CDR3, for Abs with V, encoded by VH genes from the VH7183, VHQ52, and VHS107 families but not from the VH558 family. Specificity for dsDNA was not only correlated to the presence of VH-CDR3 arginines but also to the relative position of the arginines in VH-CDR3. The majority of the VH-CDR3 arginines appeared to have been encoded by sequences generated during V-D-J recombination. These results are not only important for understanding how A specificity for dsDNA is generated but also how somatically derived structures generated during V-D-J recombination may influence clonotype selection of an immune response within an individual mouse.

Molecular analyses of anti-DNA antibodies induced by polyomavirus BK in BALB/c mice.

In the present experiments, two groups of BALB/c mice (five individuals in each group) were hyperimmunized through four consecutive immunizations with either BK virus (Group 1) or BK dsDNA complexed with methylated BSA (Group 2). All immune sera taken after the fourth immunization from both groups reacted strongly with polyomavirus BK dsDNA as well as with calf thymus dsDNA, and all sera contained antibodies that bound in the Crithidia luciliae assay. This indicates that polyomavirus BK was able to induce antibodies with binding characteristics similar to SLE anti-DNA antibodies. To further characterize these induced anti-DNA responses, 10 monoclonal anti-DNA antibodies (four from Group 1, and six from Group 2) were generated and selected for reactivity with S1-nuclease digested CT dsDNA. Their specificity for BK and CT dsDNA molecules, as well as their light and heavy chain variable region cDNA nucleotide sequences were analysed to compare them with known SLE derived anti-DNA antibodies. All of the 10 antibodies bound strongly to BK dsDNA, while seven also bound to CT dsDNA in competitive ELISA experiments. V-region analysis revealed that the induced antibodies resembled anti-DNA antibodies characteristic for murine SLE, and all but one contained arginine in the VH CDR3 region. The arginines present in the monoclonal antibodies originated either from an RF shift from RF1-->RF3 of the D-genes or from N-sequence additions. Taken together, the data demonstrate that anti-DNA antibodies in response to hyperimmunization with polyomavirus BK have the same characteristics as of those occurring spontaneously in SLE. As virus infection/replication in vivo implies expression of immunogenic (non-self) DNA-binding proteins that may render DNA immunogenic, the present results may therefore suggest one physiological mechanism for production of SLE-related anti-DNA antibodies.

Tannin - classification, analysis and applications.

This article reviews the various aspects of tannin, which is finding varied uses in leather industry and pharmaceutics.

Antigen-specific induction of antibodies against native mammalian DNA in nonautoimmune mice.

Spontaneous anti-DNA antibodies in autoimmune mice have the characteristics of antibody produced by Ag-specific, clonally selective B cell stimulation. The nature of the somatically derived antibody V region structures recurrent among spontaneous anti-DNA antibodies suggests that DNA or DNA-protein complexes may provide the antigenic stimulus for autoimmune anti-DNA antibody. In order to test this hypothesis directly, we have immunized normal, nonautoimmune-predisposed mice with complexes formed with DNA and an immunogenic, DNA-binding peptide. The highly immunogenic peptide, Fus1, forms an internal domain of a 128-amino acid ubiquitin-fusion protein from Trypanosoma cruzi. DNA-Fus1 complexes formed with native calf thymus DNA induced anti-DNA antibody in normal, nonautoimmune-predisposed mice that is similar in isotype and specificity to spontaneous anti-DNA antibody in (NZB x NZW)F1 autoimmune mice. The progressive nature of the development of dsDNA specificity in the immunized mice was also analogous to what is observed in the spontaneous anti-DNA antibody response of autoimmune (NZB X NZW)F1 mice. DNA-Fus1 immunized mice that produced IgG that bound to dsDNA had low to moderate levels of proteinuria and glomerular deposits of IgG. This experimental immunization system may be useful for understanding the immunologic basis for autoimmunity to DNA.

Structural similarity of antibody variable regions from immune and autoimmune anti-DNA antibodies.

Anti-DNA antibodies have been successfully induced in normal, nonautoimmune mice by immunization with complexes formed with a DNA-binding peptide, Fus1, and native, B form, mammalian DNA. Fus1 is a 27-amino acid peptide from the internal domain of a ubiquitin fusion protein from Trypanosoma cruzi. The structure of this peptide is homologous to the consensus amino acid sequence for a DNA-binding, "zinc finger" motif, and the peptide binds to DNA. A panel of six anti-DNA antibody-producing hybridomas, two IgM and four IgG2a, have been generated from a single BALB/c mouse immunized with Fus1-DNA. The V region structures for both H and L chains of the induced anti-DNA antibodies are highly homologous if not identical to the V region structures of spontaneous anti-DNA antibodies from autoimmune (NZB x NZW)F1 mice. The DNA specificities of the anti-DNA antibodies were also similar to those of autoimmune anti-DNA antibodies. Three of the four induced IgG antibodies bound equally well to native and denatured DNA. These results demonstrate that antibody specific for nDNA can be induced with immunogenic complexes of native DNA. They also demonstrate that monoclonal representatives of the induced anti-DNA antibodies have serologic and structural characteristics similar if not identical to those of spontaneous anti-DNA antibodies from autoimmune mice. The experimental system described here should provide insight not only about the structural basis for autoimmunity to DNA but also the function of anti-DNA antibody in the immunopathology of SLE.

Precipitating autoantibodies to mitochondrial proteins in progressive systemic sclerosis.

Sera from 88 patients with progressive systemic sclerosis were examined for precipitating mitochondrial antibodies using sonicated rat liver mitochondrial fraction as an antigen source in immunodiffusion. Precipitin lines indicating the presence of anti-mitochondrial antibodies (AMA) in 22 patients were detected. Only six of 22 sera had, additionally, precipitating antibodies to nuclear antigens. Standardized reference sera containing antibodies to mitochondrial antigens (M-A, M-B and M-C systems) were used to further characterize the type of mitochondrial antibodies. M-B antibody was most commonly detected (72.7%) either alone (eight patients) or in combination (eight patients) with M-A and M-C antibodies. M-A antibody was found in 12 patients (54.5%) and M-C antibody was present in three. The antigen related to M-B is DNAase and trypsin sensitive, in contrast to the resistant M-A antigen. AMA were detected in 21 of 22 patients by indirect immunofluorescence. When solid phase ELISA was used to detect AMA using mitochondrial fraction as antigen, a significant difference (P less than 0.005) was noted between sera with and without precipitating mitochondrial antibody. The antibody was frequently present in patients with progressive systemic sclerosis detected 2 or more years earlier (P less than 0.01). Three patients were found to have primary biliary cirrhosis and others had pruritus, hepatomegaly or abnormal liver function tests. The implication of the findings is discussed.