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

The aimof 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 from37.5 to 100% and from2.3 to 97.4% in high ionic strength buffers, respectively. In contrast, anti-U1RNP antibodies and anti-Ro/SSA antibodies lost from0 to 32.7% and from0 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 frompatients without nephropathy. Study of paired sera fromlupus nephritis patients revealed that anti-dsDNA and anti-ribosomal P antibodies frompatients 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.