LIGAND RECOGNITION BY ANTI-DNA AUTOANTIBODIES - AFFINITY, SPECIFICITY, AND MODE OF BINDING

Understanding the molecular basis of DNA recognition by anti-DNA autoa ntibodies is a key element in defining the role of antibody . DNA comp lexes in the pathogenesis of the autoimmune disorder systemic lupus er ythematosus. As part of our efforts to relate anti-DNA affinity and sp ecificity to antibody structure, and ultimately to disease pathogenesi s, we have generated a panel of eight anti-DNA mAbs from an autoimmune MRL MpJ-lpr/lpr mouse and have assessed the binding properties of the se antibodies. We find that none of our anti-DNA mAbs bind to RNA and only one low-affinity mAb cross-reacts with non-DNA antigens, albeit w eakly. None of the mAbs in our panel bind double-stranded DNA exclusiv ely. Antibodies that recognize single-stranded DNA can be categorized into two groups based on their affinity and apparent mode of binding. One group possesses relatively high affinity for oligo(dT) and may rec ognize single-stranded DNA ligands by accommodating thymine bases in h ydrophobic pockets on the antigen binding site. The second group binds more weakly, apparently recognizes single-stranded DNA nonspecificall y, and in some cases also binds double-stranded DNA. Although differen t mechanisms are used for binding single- and double-stranded ligands, the mode of DNA recognition appears conserved within groups of antibo dies.