Dual Specificity and the Formation of Stable Autoimmune Complexes

Since dual specificity at the antibody active‐site level involves new principles relative to monospecific antigen‐antibody interactions and may be a general property of autoantibodies, it was important to further characterize such antibodies. Four lupus derived autoantibodies were studied to understand parameters and mechanisms involved in the participation of dual‐specific antibody molecules in the formation of highly stable immune complexes. Because the dual‐specific binding properties of selected lupus‐related murine autoantibodies had been previously described using a solid‐phase polystyrene‐based ELISA, a conformational sensitive membrane based assay (CSI) was used on a comparative basis to further characterize NZB/NZW F1 murine monoclonal anti‐DNA autoantibodies BV 04–01 (anti‐ssDNA), BV 16–19 (anti‐ssDNA), BV 17–45 (anti‐dsDNA), and BV 16–13 (anti‐dsDNA). All four monoclonal autoantibodies exhibited anti‐IgG binding in the solid‐phase ELISA. However in the CSI assay, only anti‐dsDNA monoclonal autoantibodies BV 17‐45 and BV 16‐13 demonstrated anti‐IgG binding, while anti‐ssDNA autoantibodies BV 04–01 and BV 16–19 did not. Upon subjection to time‐dependent thermal denaturation, with and without thiol reduction at 100°C in the CSI, the self‐binding activities of BV 17–45 and BV 16–13 were abrogated demonstrating that the recognized IgG autoepitope(s) possessed conformational or discontinuous three‐dimensional properties. The immunological implications of dual specificity are discussed on a structure–function basis and its correlation with formation of pathogenic immune complexes. © 1997 John Wiley & Sons, Ltd.