Antibody avidity for native DNA in lupus nephritis.

To study the participation of the antibody avidity in the pathogenesis of lupus nephritis, we measured the antibody avidity to native DNA by the method of Minden and Farr (14) in patients with SLE. The avidity to native DNA was almost less than 40%. The avidity and the histological activity of lupus nephritis were well correlated; the antibody avidity of the active-group sera was higher than that of the inactive-group sera and the group without nephritis. In the group with antibodies of relatively high avidity, the complexes were deposited mainly in the subendothelial side of GBM and in the mesangium. On the other hand, in the group with low-avidity antibodies, the complexes were localized in the subepithelial side of GBM. On investigating the quality of the complexes, we noted that the complexes composed of high-avidity antibodies prepared in vitro were larger than those of low avidity and the former were larger than 19S. If the native-DNA-anti-native DNA system is the mechanism basic to lupus nephritis, the differences in immune response of the host, namely the degree of antibody avidity may greatly affect complex formation and influence the histological activity and nephritogenicity of lupus nephritis.