CATIONIC AND HIGH-AFFINITY SERUM IGG ANTI-DSDNA ANTIBODIES IN ACTIVE LUPUS NEPHRITIS

To investigate differences between cationic anti-dsDNA antibodies duri ng active and inactive nephritis, low- and high-affinity IgG anti-dsDN A antibodies were prepared from sera of a lupus patient and compared f or their binding affinity, spectrotype, and idiotype expression. The r atio of high-affinity to low-affinity anti-DNA antibodies and the rela tive avidity of the high-affinity anti-DNA antibodies decreased when a ctive nephritis became inactive. Isoelectric focusing showed that cati onic anti-dsDNA populations were present predominantly in the high-aff inity fraction during active nephritis and in the low-affinity fractio n during inactive nephritis. Idiotypic analysis by ELISA and Western b lotting showed that the high-affinity cationic anti-DNA antibodies dur ing active nephritis were idiotypically different from their low-affin ity counterparts during inactive nephritis. The differences in binding affinity and idiotypy of the cationic anti-dsDNA antibodies suggest t hat certain serum IgG anti-dsDNA antibodies with both cationic charge and high affinity may be associated with active nephritis.