8-oxo-7,8-dihydroguanosine triphosphate(8-oxoGTP) down-regulates respiratory burst of neutrophils by antagonizing GTP toward Rac, a small GTP binding protein.

8-oxo-7,8-dihydroguanosine triphosphate (8-oxoGTP) has been regarded simply as a oxidative mutagenic byproduct. The results obtained in this study imply that it may act as a down-regulator of respiratory burst of neutrophils. Human neutrophils treated with PMA produced superoxides and at the same time, the cytosol of these cells was intensely immunostained by 8-oxo-7,8-dihydroguanosine(8-oxoG) antibody, indicating that 8-oxoG-containing chemical species including 8-oxoGTP are produced. Human neutrophil lysates treated with PMA also produced superoxides, which was stimulated by GTPgammaS but inhibited by 8-oxoGTPgammaS. Moreover, 8-oxoGTPgammaS suppressed the stimulatory action of GTPgammaS. Likewise, GTPgammaS stimulated Rac activity in neutrophil lysates but 8-oxoGTPgammaS and GDP inhibited it. The inhibitory effect of GDP was one tenth that of 8-oxoGTPgammaS. Here again, 8-oxoGTPgammaS also suppressed the stimulatory action of GTPgammaS on Rac activity. These results imply the possibility that 8-oxoGTP is formed during respiratory burst of neutrophils and limits neutrophil production of superoxides by antagonizing GTP toward Rac.

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.

Antibodies to guanylic acid: fractionation and specificities.

Guanylic-acid-specific antibodies were elicited in rabbits, using as immunogen pG linked through 5'-phosphate to thyroglobulin. Specificity and affinity of antibodies to nucleotides, nucleosides, DNA, and RNA were studied by their binding to radioactive ligands and competition experiments. Guanylic-acid-specific antibodies do not bind to deoxyguanylic acid and have an average association constant of 10(7) M-1 at 4 degrees C. Binding of the antibodies to 3H-RNA is G-specific. The antibodies do not bind to 32P-ssDNA or 32P-dsDNA. The pG-specific antibodies could be separated into different fractions by affinity chromatography. These fractions, though specific to pG, differ in their cross-reactivities to nucleosides and nucleotides.

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.

Base specific binding of deoxyguanylate and deoxycytidylate antibodies to double stranded DNA.

Antibodies raised in rabbits against deoxyguanylate and deoxycytidylate bind to 3H-lambda double stranded DNA and the binding is base specific. The concentrations of antibody populations that bind to double stranded DNA are much less than those binding to denatured DNA. Due to their low concentrations, these antibodies were not detected in earlier studies. These antibodies are expected to be useful to probe the conformational flexibilities of double stranded DNAs.