The effect of anti-Z-DNA antibodies on the B-DNA-Z-DNA equilibrium

Four different preparations of rabbit and goat anti-Z-DNA antibodies were examined to determine the effects of antibody binding on the B-DNA-Z-DNA equilibrium. One of the four antibodies, a goat IgG, caused a marked lowering in the ionic strength required for the B-DNA to Z-DNA transition in poly(dG-dC) X poly(dG-dC), shifting the midpoint from 2.25 to 2.0 M NaCl. This IgG had a more prominent high affinity antibody population than did the other goat IgG, which caused little change in the midpoint of this transition. The presence of anti-Z-DNA antibodies also reduced the degree of negative supercoiling required for the formation of Z-DNA in (dG-dC)n sequences inserted into closed circular plasmid DNA. The goat IgG with the more marked effect on the salt-induced transition also had a greater effect in favoring Z-DNA formation in negatively supercoiled plasmids. A shift toward Z-DNA formation was observed in circular dichroism measurements upon antibody binding to poly(dG-dC) X poly(dG-dC) in very low ionic strength solution as well. We propose that the stabilization of Z-DNA by antibody binding in poly(dG-dC) X poly(dG-dC) occurs cooperatively, several antibody molecules binding to a single polymer molecule and stabilizing the entire molecule in Z-DNA through their combined binding energies. The stabilization of Z-DNA by antibody binding in a supercoiled plasmid can be significant, and failure to consider this effect and to choose appropriate conditions for measurement can lead to errors in estimating when Z-DNA will form in response to negative supercoiling.

Antigenicity, catalytic activity and conformation of Agaricus bisporus tyrosinase: interaction of conformation-directed antibodies with the native and irradiated enzyme

The antiferromagnetically spin-coupled Cu2+ pair present in the active center of tyrosinase was found to be indispensable for its catalytic function. However, the metal ion did not contribute to the conformational integrity or antigenicity of the enzyme molecule. Irradiation of tyrosinase with 254 nm light resulted in dose dependent, essentially irreversible losses of its catalytic and antigenic functions. The apparent first order rate constants for the two processes were 17.6 X 10(-2) min-1 and 28.1 X 10(-2) min-1, respectively. The approximately 1.6-fold difference between the two rate constants suggests that the sites of antigenic determinants in tyrosinase are distinguishable from the enzymic active site by their higher photosensitivity. Kinetic analysis of the data as to photoinactivation, and the UV induced losses of antigenicity and structural integrity revealed that UV radiation disrupts the short-range noncovalent interactions occurring within the enzyme molecule. The disruption of the noncovalent interactions results in partial unfolding of the tyrosinase structure which in turn leads to the progressive loss of its catalytic activity and antigenicity. The anti-tyrosinase antibodies raised in rabbits were found to be directed against the native conformation of the enzyme. It is speculated that these antibodies might be useful in exploring the tyrosinase conformation and in studying the effects of various factors on the enzyme surface and molecular structure.

Binding of monoclonal anti-native DNA autoantibodies to DNA of varying size and conformation

A microchemical assay for phosphorus was applied to the measurement of DNA in immune complexes formed with monoclonal or serum anti-DNA autoantibodies and DNA of varying size and conformation. Two monoclonal antibodies were produced by hybridomas derived from spleen cells of autoimmune MRL-lpr/lpr mice and were purified from culture fluid by affinity chromatography on columns of goat anti-mouse Ig-Sepharose. Double-helical DNA fragments were prepared by brief digestion of calf thymus DNA with micrococcal and S1 nucleases and fractionation on Sepharose 4B; their double-stranded structures was confirmed by measurement of thermal denaturation. Immune complexes were formed with monoclonal or serum antibodies and native DNA or DNA fragments or denatured DNA; the complexes were precipitated with goat anti-mouse IgG and washed, and DNA phosphorus content of the precipitates was measured. With one monoclonal autoantibody (H241), there were discontinuous increases in the amount of DNA that could be bound (and decreases in the antigen concn required for half-maximal binding) as the DNA size increased. There were especially marked increases in binding efficiency as fragment size increased from an average of 100 (range 85-105) to an average of 150 (range 105-170) base pairs, and again between 450 (range 360-620) and 600 (range 425-825) base pairs. A second monoclonal antibody (H143) did not show significant variation in binding with DNA fragments larger than 300 base pairs. With smaller fragments, the amount of DNA bound by H143 was reduced, but the DNA concn required for half-maximal binding was not. Affinities of these monoclonal antibodies were within the spectrum of human systemic lupus erythematosus serum IgG anti-DNA autoantibodies. The dependence of binding on mol. wt is important in the evaluation of these monoclonal antibodies as biochemical reagents and as potential participants in formation of immune complexes in vivo.

Isolation of the first trypsin inhibitor from the genus Aspergillus

The fungus Aspergillus flavipes was grown on a Czapeck sucrose medium; the biomass so obtained was treated with high concentration of sucrose to release intracellular metabolites. Sephadex G-75 chromatography of the latter yielded a pure protein having anti-trypsin activity in vitro.

Fluorometric assay for anti-DNA antibodies: use of ethidium bromide as intercalating dye

Autoantibodies against double-stranded DNA in the sera of patients with various autoimmune diseases have been examined by fluorometric assay using ethidium bromide as intercalating dye. Forty-three per cent of SLE patients, 14% of SLE patients with overlapping PSS, 20% of PSS patients and none of the RA and SS patients were positive for anti-DNA antibodies. The method was found to be more sensitive than immunoprecipitation techniques and comparable with the hemagglutination assay. The technique is simple, sensitive, specific and can be employed for the detection of low concentration of anti-DNA antibodies.

Fluorescence studies on the interaction of furocoumarins with DNA in the dark

The dark interaction of furocoumarins with DNA has been studied by a fluorescence quenching technique. The intrinsic fluorescence of psoralen, 4,5', 8-trimethylpsoralen (TMP) and 8-methoxypsoralen (8-MOP) was quenched to an appreciable extent upon their noncovalent binding to DNA molecule. The analysis of the binding data revealed that TMP binds to DNA with higher efficiency than 8-MOP and psoralen, their apparent Scatchard binding constants being 13.2 X 10(5) M-1, 7.1 X 10(5) M-1, and 12.2 X 10(5) M-1, respectively. The interaction of furocoumarins with DNA was strongly dependent on the conformational stability of DNA in the particular interaction media. The perturbation of DNA structure by changing the ionic environment decreased its interaction with furocoumarins. However, the interaction was facilitated by the presence of an electron-donating moiety in the parent compound, psoralen.

Antibodies from patients with mixed connective tissue disease react with heterogeneous nuclear ribonucleoprotein or ribonucleic acid (hnRNP/RNA) of the nuclear matrix

The sera of patients with mixed connective tissue disease (MCTD) have high titers of antibodies directed against nuclear U1-ribonucleoprotein (U1-RNP). This antigen is easily extracted from nuclear preparations with physiologic saline and from tissue sections with 0.1 HCl, leaving the nucleic acids and nuclear matrix behind. When U1-RNP is extracted from HEp-2 cells with 0.1 N HCl, the sera of 32/32 patients with MCTD react with another antigen that is exposed by the extraction procedure. This antigen is not destroyed by trypsin and deoxyribonuclease 1 treatment but is sensitive to both purified ribonuclease A and purified micrococcal nuclease. Absorption studies showed that the antibody reacting with this antigen cannot be absorbed by sheep red blood cells coated with extracts of rabbit thymus that contain U1-RNP. Radioimmunoassay showed that the reaction of the unadsorbed antibody was with heterogeneous nuclear ribonucleoprotein or ribonucleic acid (hnRNP/RNA) and not with transfer RNA or ribosomal RNA. The hnRNP/RNA antigen is demonstrated as discrete particles in the internucleolar chromatin of interphase cells, but in metaphase cells the antigen is diffusely dispersed. The distribution, solubility, and biochemical characteristics suggest that the antigenic moiety is part of the nuclear matrix. Therefore, MCTD sera contain antibodies that react with at least two species of nuclear RNP: small nuclear RNP (snRNP), as described by others, and a high m.w. hnRNP/RNA bound to the nuclear matrix.

Antibodies from patients with mixed connective tissue disease react with heterogeneous nuclear ribonucleoprotein or ribonucleic acid (hnRNP/RNA) of the nuclear matrix

The sera of patients with mixed connective tissue disease (MCTD) have high titers of antibodies directed against nuclear U1-ribonucleoprotein (U1-RNP). This antigen is easily extracted from nuclear preparations with physiologic saline and from tissue sections with 0.1 HCl, leaving the nucleic acids and nuclear matrix behind. When U1-RNP is extracted from HEp-2 cells with 0.1 N HCl, the sera of 32/32 patients with MCTD react with another antigen that is exposed by the extraction procedure. This antigen is not destroyed by trypsin and deoxyribonuclease 1 treatment but is sensitive to both purified ribonuclease A and purified micrococcal nuclease. Absorption studies showed that the antibody reacting with this antigen cannot be absorbed by sheep red blood cells coated with extracts of rabbit thymus that contain U1-RNP. Radioimmunoassay showed that the reaction of the unadsorbed antibody was with heterogeneous nuclear ribonucleoprotein or ribonucleic acid (hnRNP/RNA) and not with transfer RNA or ribosomal RNA. The hnRNP/RNA antigen is demonstrated as discrete particles in the internucleolar chromatin of interphase cells, but in metaphase cells the antigen is diffusely dispersed. The distribution, solubility, and biochemical characteristics suggest that the antigenic moiety is part of the nuclear matrix. Therefore, MCTD sera contain antibodies that react with at least two species of nuclear RNP: small nuclear RNP (snRNP), as described by others, and a high m.w. hnRNP/RNA bound to the nuclear matrix.

Inhibition of human serum RNase activity by aurine tricarboxylic acid polymer: effect on the antigen-antibody reaction

The structural integrity of RNA as antigen in immunological reactions with serum as the source of antibody is endangered because of RNase activity. Aurine tricarboxylic acid (ATA) in its polymeric form has been used to overcome this problem by inhibiting serum RNase. At low concentrations, the polymer completely arrests the RNA degrading activity. An appreciable increase in antibody activity was observed with an anti-RNA serum pretreated with ATA polymer.

Detection of anti-RNA antibodies in systemic lupus erythematosus by ELISA using nylon as solid support

A highly sensitive and reproducible enzyme-linked immunosorbent assay (ELISA) for the detection of anti-RNA antibodies is described. The assay procedure involves adsorption of total cellular RNA on nylon beads which could be conveniently stored for a considerable period of time without loss in antigenicity. Sixty-four percent of systemic lupus erythematosus (SLE) sera were positive for anti-RNA antibodies with fluorogenic substrate against 48% with colorigenic substrate.

Identical specificity of lupus antibodies and antibodies elicited in rabbits against Sm and RNP antigens

Rabbits immunized with purified Sm and RNP small nuclear ribonucleoproteins (snRNPs) produced precipitating and hemagglutinating antibodies against these antigens. These antibodies had immunological specificity identical to the naturally occurring SLE anti-Sm/RNP antibodies as demonstrated by immunoprecipitation results and studies involving the characterization of immunoaffinity purified antigens isolated from the rabbit immune and SLE anti-Sm/RNP IgG affinity columns.

Purification and identification of antigenic polypeptides of Sm and RNP antigens of goat liver

A ribonucleoprotein complex containing Sm and RNP antigenic activity was isolated from goat liver. The sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed the complex to contain four major polypeptides of 80,000, 70,000, 30,000 and 14,000 molecular weights. When the gels were probed for antigenic polypeptides by an enzyme-linked immunosorbent assay and fluorescent antibody method, anti-Sm sera were found to react with polypeptides of 14,000 and 30,000 molecular weights whereas anti-RNP sera recognized 70,000 and 80,000 molecular weight polypeptides with minor reactivity in the polypeptide of 14,000 molecular weight. Sera containing antibodies to both Sm and RNP reacted with all the four polypeptides.

Nutritional survey of Bangladeshi children aged under 5 years in the London borough of Tower Hamlets

The main deficiencies in the diet of Bangladeshi infants and children are vitamin D, iron, and later, calories. Protein intake is a little low in some, but in general is satisfactory. Calcium and vitamin C intakes are adequate. The proportions of food are often inappropriate, mainly because of a high carbohydrate intake. Weaning tends to be late, with predominant milk drinking, even into the second year of life. Convenience baby foods, containing mainly carbohydrate are the major components of the diet until well into the second and third years of life, without the conversion to family food seen in white children. Vitamin D is given to fewer than half the children. It may be given to fewer still if the observation that bottles were often unopened is true for many families.

Enzyme-linked immunosorbent assay for detection of antibodies to extractable nuclear antigens in systemic lupus erythematosus, with nylon as solid phase

In this enzyme-linked immunosorbent assay (ELISA) for detection of antibodies against extractable nuclear antigens (ENA) in sera of patients with systemic lupus erythematosus (SLE), nylon is used as solid phase for antigen binding instead of the commonly used polystyrene surface. Optimal conditions for activation of the nylon beads, antigen coating, and other relevant factors have been investigated. We compared the incidence of anti-ENA antibodies in SLE, using chromogenic and fluorogenic enzyme substrates. Of SLE patients, 54% were positive for anti-ENA antibodies when chromogenic substrate was used as compared with 68% for fluorogenic substrate. Antibody activity against Sm and RNP antigens was distinguished on the basis of ribonuclease sensitivity of the RNP antigen. The method described offers advantages such as decreased background activity, increased surface area, facility for prolonged storage of antigen-coated solid phase, and miniaturization of the assay.

Enzyme-linked immunosorbent assay for detection of antibodies to extractable nuclear antigens in systemic lupus erythematosus, with nylon as solid phase

In this enzyme-linked immunosorbent assay (ELISA) for detection of antibodies against extractable nuclear antigens (ENA) in sera of patients with systemic lupus erythematosus (SLE), nylon is used as solid phase for antigen binding instead of the commonly used polystyrene surface. Optimal conditions for activation of the nylon beads, antigen coating, and other relevant factors have been investigated. We compared the incidence of anti-ENA antibodies in SLE, using chromogenic and fluorogenic enzyme substrates. Of SLE patients, 54% were positive for anti-ENA antibodies when chromogenic substrate was used as compared with 68% for fluorogenic substrate. Antibody activity against Sm and RNP antigens was distinguished on the basis of ribonuclease sensitivity of the RNP antigen. The method described offers advantages such as decreased background activity, increased surface area, facility for prolonged storage of antigen-coated solid phase, and miniaturization of the assay.