Abstract
The origin and relative biological importance of the many different DNA-reactive antibodies that appear in systemic lupus erythematosus are not well understood. A detailed analysis of their fine specificity and binding characteristics with DNA is a necessary step in understanding their biology. We have examined here two monoclonal antibodies (mAb) IV-228 and V-88 that are, respectively, characteristic of antibodies, which bind exclusively to single-stranded (ss) DNA and to both double-stranded (ds) DNA and ssDNA. By surface plasmon resonance (SPR) on BIAcore, we characterized the kinetics of binding of each antibody to synthetic ss and ds oligonucleotides. Antibody V-88 and IV-228 showed different patterns of reactivity for both ss and ds oligonucleotides, characterized by distinctly different kinetic parameters. Analysis of their binding kinetics indicates the importance of base composition in defining DNA epitopes, and shows that some epitopes, such as that recognized by mAb V-88, are expressed on dsDNA and ssDNA, whereas others, as recognized by IV-228, are not. The base preferences of V-88 for ds GC-rich structures over AT-rich, and of IV-228 for ss T-rich structures, also reveal distinct differences between these antibodies. We conclude that the different binding properties of the antibodies will relate to their biological activities. The base preferences of the antibodies suggest that they might be induced by different immunological stimuli, such as those that could be provided by the various DNA fragments and structures released during programmed cell death.