Evidence for sequence-specific recognition of DNA by anti-single-stranded DNA autoantibodies

Anti-DNA autoantibodies are a serological hallmark of the autoimmune disorder systemic lupus erythematosus. In a process involving antigen recognition, these antibodies are also believed to mediate the kidney inflammation that results in much of the morbidity and mortality associated with lupus. However, the nature of specific DNA antigens recognized by anti-DNA and the way in which anti-DNA interact with these molecules remains poorly understood. As a first step in defining the molecular basis of anti-DNA interactions, binding site selection experiments were conducted using three clonally related murine monoclonal anti-ssDNA autoantibodies previously isolated from a lupus prone MRL-lpr mouse (Swanson, P. C., Ackroyd, P. C., and Glick, G. D. (1996) Biochemistry 35, 1624-1633). Studying the interaction of these autoantibodies with the selected sequences (and variants) through affinity measurements and footprinting experiments provides evidence for sequence-specific binding of ssDNA. However, despite the similarity in amino acid sequence between the three mAbs, only mAb 11F8 appears to possess sequence specificity. The salient features of the interaction between 11F8 and its selected sequence (e.g., limited dependence of ionic strength upon binding, cross-reactivity, and conformational complementarity) are best described by combining the paradigms invoked to explain protein.nucleic acid and antibody.antigen recognition.