Dual binding capabilities of anti-double-stranded DNA antibodies and anti-ribosomal phosphoprotein (P) antibodies.

The aim of this study is to identify distinctive properties of pathogenic anti-double stranded DNA antibodies and anti-ribosomal P antibodies. The binding activity of anti-dsDNA and anti-ribosomal P antibodies to their cognate antigens in 0.15 M and 1.5 M NaCl solutions on ELISA was examined. All anti-dsDNA and anti-ribosomal P antibodies exhibited a loss of their binding activity from 37.5 to 100% and from 2.3 to 97.4% in high ionic strength buffers, respectively. In contrast, anti-U1RNP antibodies and anti-Ro/SSA antibodies lost from 0 to 32.7% and from 0 to 40.1% of their binding activity, respectively. Anti-dsDNA and anti-ribosomal P antibodies from patients with nephropathy showed significantly higher binding activity in high ionic strength buffers than those from patients without nephropathy. Study of paired sera from lupus nephritis patients revealed that anti-dsDNA and anti-ribosomal P antibodies from patients during disease flare show stronger binding activity in high ionic strength buffer than those during remission. Most anti-dsDNA and anti-ribosomal P antibodies bind their antigens by ionic interactions that are sensitive to high salt. Such dual binding capability of anti-dsDNA and anti-ribosomal P antibodies may underlie their multiple cross reactivities to various epitopes and help elucidate the pathogenic potential of autoantibody subsets.