Specificity of mouse hybridoma antibodies to DNA. III. Antigenic determinants of nucleic acids recognized by poly(dG) specific monoclonal antibodies.
Immunochemical properties of monoclonal autoantibodies to single stranded DNA (ssDNA), which were derived from systemic lupus erythematosus (SLE) prone mice and were specific for poly(dG), were studied using a hapten inhibition assay with oligo- and mononucleotides. Deoxyguanosine monophosphate (dGMP) completely inhibited the ssDNA binding of poly(dG) specific monoclonal antibodies. The affinity to deoxyguanosine was approximately 70% of dGMP, and to guanosine monophosphate (GMP) and to guanosine was 38% and 24%, respectively. In contrast, other purine monomers such as deoxyadenosine monophosphate (dAMP), adenosine monophosphate (AMP) and adenosine exhibited virtually no inhibitory effect on the ssDNA binding of these monoclonal hybridoma autoantibodies. By the same competitive inhibition enzyme immunoassay using deoxyguanosine oligonucleotides of various chain lengths, the minimal antigenic size of ssDNA encompassed by the combining site of the Fab portion of anti-ssDNA monoclonal autoantibodies was determined to be the tetra- or pentanucleotide.