Anti-sDNA antibody purified from sera of human patients with systemic lupus erythematosus--II. Ligand binding properties of purified antibodies

Specificity of anti-DNA antibodies in SLE-I. Definition and gross specificity of antibody populations in human SLE plasma

Populations of anti-DNA antibodies in two SLE plasma were defined based on their patterns of reactivity in inhibition assays with single and double-stranded DNA as well as mono- and oligonucleotides. Two populations of anti-DNA antibodies were seen in both plasma tested. The first population reacted specifically with ssDNA and was inhibited by relatively low concentrations of free nucleotides indicating that it recognized the nucleotide bases in ssDNA. The second population bound both ss and ds calf thymus DNA with apparent equal affinity. The cross-reactive anti-DNA antibodies were inhibited by mononucleotides (at high concentrations) and by single-stranded oligonucleotides (average length tetranucleotides). For one of the plasma tested (PS), pBR322 plasmid DNA (54% G + C) was a significantly more effective inhibitor than calf thymus DNA (39% G + C). These results suggested that nucleotide bases contributed to dsDNA binding by cross-reactive anti-DNA antibodies.

Generation and characterization of three murine monoclonal nucleotide binding anti-ssDNA autoantibodies

Three murine monoclonal anti-ssDNA autoantibodies have been produced by fusion of spleen cells from NZB/NZW F1 hybrid mice with Sp 2/0-Ag 14 murine myeloma cells. Specificity studies characterizing monoclonal anti-ssDNA autoantibodies revealed binding patterns for nucleotides. Clone E-4-1 showed preferential binding with mono-, di- and polyguanosine. Clones E-4-4 and E-11-1 specifically bound mono-, di- and polythymidine. Results of inhibition studies indicated an order of reactivity for each monoclonal autoantibody: polynucleotide greater than dinucleotide greater than mononucleotide. In a fluorescence immune assay, using aminonaphthyl derivatives of nucleotides, all three monoclonal antibodies exhibited a low affinity (5 x 10(4)-10(5) M-1) for the homologous mononucleotides. The affinity of clone E-4-1 increased approximately 10-fold when a dinucleotide derivative was used relative to a mononucleotide fluorescent ligand.

Monoclonal murine anti-nucleic acid antibody with double-stranded specificity

The NZB/NZW F1 murine model for the autoimmune disease systemic lupus erythematosus (SLE) has been employed in somatic cell hybridizations to develop hybridoma autoantibodies with double-stranded (ds) DNA specificity. Monoclonal anti-DNA antibodies from one hybridoma cell line were purified and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing. Results of comparative binding studies with tritiated [3H]-colicin E1 plasmid DNA probes suggested preferential binding for the native DNA conformation relative to single-stranded DNA. [3H]dsDNA binding was inhibited by several ribohomopolymers (poly G, U and I) but not by free nucleotides, indicating that the phosphodiester-ribose backbone may contribute to the binding specificity of the clonotype.

Colicin E1 plasmid as a probe for detection and study of anti-dna activity in SLE sera

Tritiated colicin E1 plasmid DNA ([3H]DNA) was purified, characterized and developed as a test antigen for study of anti-DNA antibody activity in a modified Farr assay. The homogeneous molecular weight (4.2 X 10(6) daltons), physical state (intact covalently closed circles), and capacity for intrinsic radioactive labeling to a suitable specific activity were all important properties of the plasmid probe. In addition, the ability of the Farr assay to measure primary antigen/antibody interactions made quantitative determinations of anti-double-stranded DNA (dsDNA) antibody activity possible. Sonication of the plasmid resulted in definable fragments which were thermally denatured and used in the measurement of anti-single-stranded DNA (ssDNA) antibody activity. Results from studies in which unlabeled dsDNA, ssDNA, amd free 2'-deoxyribonucleotides were employed to inhibit binding of [3H]DNA by anti-DNA antibodies indicated the presence of 3 distinct anti-DNA specificities in SLE sera.