Resolution of rabbit polyclonal anti-fluorescein Fab (IgG) fragments into subpopulations differing in affinity and spectral properties of bound ligand

Fab fragments derived from ten different IgG populations of hyperimmune rabbit polyclonal anti-fluorescein antibodies were further resolved into subfractions based on differences in time-dependent dissociation from an FITC-adsorbent in the presence of 0.1 M fluorescein at 4 degrees C. Fab fragments separated into subpopulations based on specific dissociation times of 0.1 day, 1.0 day, 10 days and 100 days from the adsorbent. Finally, after the 100 days elution step incubation with 6.0 M guanidine-HCl was included to determine total protein concentration of specific anti-fluorescein Fab fragments. Yields of specifically eluted Fab fragments ranged from 12.7 to 84.1% of the total Fab population originally incubated with the adsorbent. All Fab polyclonal populations and subpopulations analyzed quenched the fluorescence of the bound ligand by 90% or greater. None of the plots of protein concentration versus percent yield of the total specific antibody obtained for each of the five resolved fractions constituting a specific polyclonal population conformed to Gaussian distributions. All resolved Fab subpopulations retained bound fluorescein ligand that exhibited significant bathochromic shifts in absorbancy. Based on the extent of the red-shift the antibodies segregated into one of two general spectral families showing either a peak shift to 505-507 nm or to 518-520 nm. The red-shift to 518-520 nm appeared unique to rabbit anti-fluorescein antibodies, since corresponding large shifts have not been observed with antibodies derived from other species (e.g. mouse, rat, chicken, etc.). K(d) values determined for the resolved fractions confirmed a continuous progression in affinity from the 0.1day through the 100 days elution. Preliminary isoelectric focusing analyses revealed progressive selection for relatively more homogeneous fractions, especially in the 100 days resolved fraction.     

Elution of kidney-bound antibody by pH-shift does not discriminate between antibodies differing in functional affinity for their ligand

Antibodies eluted from kidneys by traditional methods of pH shift have been used as reagents in a wide variety of experimental analyses without knowledge of whether their ligand affinity influenced their removal from parenchymal tissue. In the current study we employed two monoclonal antibodies, differing only in their functional affinity (high; K = 2.1 x 10(8)/M and low; K = 6.2 x 10(6)/M) to a common ligand found on the renal basement membrane, to evaluate whether a standard elution technique might selectively facilitate the removal of one antibody over the other. Our findings indicate, however, that the routine methods of elution by pH shift remove both antibodies equally well (41-48%), and without loss of paratypic function. These results provide new evidence that elution by pH shift can produce eluate antibodies which are not biased by preferred affinities.     

Anti-ribosomal antibodies from lupus patients bind DNA

Antibodies specific for ribosomal P proteins (anti-P) are a hallmark of systemic lupus as anti-DNA antibodies are. It has been reported that anti-P antibodies are more frequently detected in anti-dsDNA positive sera. The aim of the present study was to verify the binding ability of anti-P antibodies towards polynucleotides and nucleosomes. We purified anti-P antibodies from 8 SLE patients' sera and we analysed them by ELISA on plates coated with DNA or nucleosomes. We performed also inhibition experiments in order to verify the specificity of the binding. All the purified anti-P antibodies bound DNA, but some anti-DNA binding activity remained among the non-anti-P antibodies in the flow through. Only half of the purified antibodies bound to nucleosomes, and anti-nucleosomal activity was demonstrated also in non anti-P antibody fraction. The inhibition experiments performed on two anti-P antibodies pointed out that only the homologous antigen inhibited the binding to either P peptide or DNA coated onto the solid phase. These results show that sera in which the two specificities coexist contain antibodies endowed with a double binding ability for DNA and the P peptide.     

Antibody diversity in amphibians. Noninbred axolotls used the same unique heavy chain and a limited number of light chains for their anti-2,4-dinitrophenyl antibody responses

Noninbred axolotls (Ambystoma mexicanum, amphibia, urodela) were immunized with trinitrophenylated sheep red blood cells (TNP-SRBC) and anti-2,4-dinitrophenyl (DNP)/TNP antibodies were individually purified by affinity chromatography. The isolated IgM-like antibodies were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) under reducing conditions. The SDS-PAGE and IEF-separated heavy (H) and light (L) chains were electroblotted onto nitrocellulose, probed with mouse monoclonal antibodies specific for H or L axolotl Ig chains and stained by a rabbit anti-mouse Ig horseradish peroxidase conjugate. The specific detection of axolotl anti-DNP/TNP H chain spectrotypes shows for each of the 14 individually analyzed samples a very similar pattern of 4-5 ordered spaced bands. This suggests that all animals express the same VH chain segment representing the germinal expression of a unique VH gene. When the same analysis was performed starting from a pool of nonimmunized axolotl sera, a low background of natural anti-DNP antibodies was detected. When analyzed by IEF, the H chains of the pooled anti-DNP natural antibodies display the same pattern of restricted heterogeneity when compared to the H chain spectrotypes of the individual immune anti-DNP/TNP antibodies. The specific detection of the axolotl anti-DNP/TNP L chain spectrotypes indicates at the individual level more heterogeneous and polymorphic patterns compared with H chains, although most animals share the majority of their bands. Our experiments indicate that in axolotl, the production of antibodies to DNP results from the germinal expression of a very limited set of V genes, already expressed as naturally occurring anti-DNP antibodies before immunization. This seriously restricts the possible extension of the antibody repertoire and perhaps even the nature of antibody "specificity" in this primitive vertebrate.     

Heterogeneity in anticatalytic activity of antibody specific for horseradish peroxidase

Rabbit antibodies specific for horseradish peroxidase are heterogeneous in their ability to inhibit enzyme activity. Heterogeneity was demonstrated by fractionation of the total antiperoxidase pool by differential ammonium sulfate precipitation and differential elution of antibody from enzyme affinity columns. Both fractionation methods yielded antibody subpopulations that differed in anticatalytic activity. Some antibody subpopulations decreased enzyme activity almost completely at low molar ratios of antibody to peroxidase. Other subpopulations were not effective inhibitors even at great molar excess. Admixture experiments demonstrated that inefficient antibody pools decreased the anticatalytic effect of highly inhibitory antibody. The degree of inhibition observed with unfractionated antiserum is a reflection of the interaction of various antibody subpopulations with the enzyme. No correlation was found between the immunoglobulin class of antiperoxidase and anticatalytic efficiency in analyses of numerous antisera. The determinant specificity of an antiperoxidase molecule determines its anticatalytic ability. A peptide fragment (mol. wt 22,500) of peroxidase prepared by partial tryptic digestion bount 60 to 70% of the total antiperoxidase in a number of antisera. However, the peptide did not bind inhibitory antibodies.     

A Solid Phase Enzyme-linked Immunosorbent Assay (ELISA) for the Demonstration of Antibodies against Denatured, Single-stranded DNA in Patient Sera

A solid phase enzyme-linked-immunosorbent assay (ELISA) for the determination of antibodies against denatured, single-stranded (ss-) DNA is described. Polystyrene cuvettes coated with ss-DNA were incubated with serum samples and the anti-ss-DNA antibodies bound were detected by means of an anti-IgG-alkaline phosphatase conjugate. The binding of anti-ss-DNA antibodies in individual sera was expressed as units calculated as % of the absorbance in relation to the absorbance value obtained with a reference pool. Absorption experiments showed that the assay is specific for antibodies against denatured DNA. By using immunologically purified anti-ss-DNA antibodies the assay was shown to detect specific antibodies in concentrations down to 1 ng/ml. Antibodies against DNA could be detected in 94% of sera with antinuclear antibodies.     

Specific removal of anti-A and anti-B antibodies by using modified dialysis filters

Removal of anti-A and anti-B blood group antibodies from human blood has been shown to facilitate cross-matched kidney transplantation by preventing hyperacute rejection. Patients in these studies had anti-A and anti-B antibodies removed by using plasmapheresis, followed by immunoadsorption onto packed bead columns. We conducted a study to assess the feasibility of selectively removing anti-A and anti-B antibodies directly from blood by using modified dialysis filters. An anti-A and anti-B specific antigen was covalently attached to the lumenal surfaces of hollow fibers within selected commercial dialysis modules. The filters were able to reduce the anti-A and anti-B titers of 300 ml of blood to 2 or below. A low molecular weight fraction of our antigen system was found to have no antibody binding capacity. The standard antigen was purified by removal of the low molecular weight fraction and a dialysis filter was modified by using the purified antigen. This filter displayed a six-fold higher capacity than a dialysis filter modified with the same mass of standard antigen. We conclude that selective blood group antibody removal by antigen modified dialysis filters is feasible and may be a simpler system than plasmapheresis followed by immunoadsorption.     

IgA polyspecific autoantibodies in IgA nephropathy.

The specificity of circulating and kidney-bound IgA during IgA nephropathy is still a matter of discussion. In the present study, high levels of IgA antibodies directed against a panel of self and non-self antigens were found in the serum from patients with IgA nephropathy and were eluted from four out of the seven kidney biopsies studied. After immunoadsorption of pooled selected serum samples on TNP and actin-coated columns, polyspecific IgA antibodies were eluted. This supports the hypothesis that IgA-bearing B cells clones most probably producing polyspecific antibodies are a major feature of human IgA nephropathy. These findings also suggest that it may be hazardous to draw conclusions from the finding of apparently monospecific IgA antibodies in this condition.     

Anticryptococcal type D antibodies raised in rabbits

Antibodies to Cryptococcus neoformans Type D have been raised in rabbits. The partially purified antibody pool was fractionated by affinity-chromatography, and it was shown that antibodies to the capsular polysaccharide of Type D were present in the pool. Neither methyl α-d-mannopyranoside, nor d-mannose were inhibitors of the binding of Type D polysaccharide to the antibody-pool. Thus it appears that the serum contains antibody populations which are specific for terminal side-chain carbohydrate moieties of the immunizing antigen.     

Natural autoantibodies in systemic lupus erythematosus.

We have tested the sera of 25 patients with systemic lupus erythematosus (SLE) for antibody activity against a panel of six antigens: DNA, TNP, actin, tubulin, myosin, albumin. Eluates from renal biopsy tissue were also tested. Sera from patients with lupus nephritis were found to contain high titres of IgA antibodies directed against the antigens of the panel, and marked IgG anti-DNA and anti-TNP antibody activity. The IgG anti-TNP antibodies isolated from SLE serum by affinity chromatography on a TNP-immunoadsorbent, were also found to possess anti-DNA activity. Kidney eluates obtained from biopsy specimens of SLE patients contained IgG antibodies strictly specific for DNA in three out of the nine patients tested, while three eluates from the remaining six patients reacted with DNA and TNP and three with DNA and all the other antigens of the panel. These results strongly suggest that in SLE sera there are at least three populations of circulating anti-DNA antibodies: those strictly specific for DNA, those recognizing DNA and TNP and those recognizing DNA and other macromolecules. Furthermore, because six out of nine of the eluates contained antibodies with an absolute or restricted specificity for DNA, this suggests that these antibodies are more often pathogenic than the polyspecific ones recognizing DNA and other macromolecules.     

Quantitative flow cytometric and clonogenic evaluation of glass bead affinity fractionation of antibody-labeled murine bone marrow

Monoclonal antibodies and a glass bead affinity fractionation technique were used to selectively deplete subpopulations of murine bone marrow cells. Flow cytometric analyses permitted quantitative measurement of subpopulation depletion and characterization (light scatter and fluorescence intensity) of both the eluted and bound cell subpopulations. Mouse bone marrow cells were labeled with selected monoclonal rat anti-mouse antibodies directed against cell surface antigens and were eluted through a glass bead column coated with goat anti-rat immunoglobulin. Unlabeled cells passed through the column, whereas cells labeled with the antibody were selectively retained. Column operating conditions for optimal depletion of labeled cells were determined. With specific column conditions, 97% of the antibody positive cells were retained on the column. In addition, clonogenic assays on cells sorted from unfractionated and column fractionated preparations provided estimates of the fraction of granulocyte macrophage progenitors (CFU-GM) in the different cell subpopulations. The enrichment of CFU-GM achieved in the eluted cell populations was dependent upon the antibody used for cell labeling and ranged from four- to six-fold. Since large numbers of cells can be processed rapidly, this technique, in combination with antibodies specific for non-clonogenic cells, is particularly suitable when preparations enriched in colony-forming progenitors are required.     

Immunostimulatory effect of cis-diamine dichloroplatinum (II)

Cis-diamine dichloroplatinum (II) (DDP) injected i.p. or i.v. at the dosage of 0.83 mg/kg to BALB/c mice on days 0, 7 and 14 elicited antibodies against proteins (RSA, BGG) and haptens (TNP, FITC) detectable by ELISA or by passive haemagglutination. Significant increase in antibody production was observed with either route of DDP application. A similar set of antibodies against antigens which do not cross-react with the immunizing proteins was observed when mice were immunized with complexes formed by an in vitro incubation of RSA and BGG with DDP. Thus, proteins modified in vivo or in vitro by DDP may stimulate the production of antibodies of unexpected specificities.     

Separation and characterization of anti-benzylpenicilloyl (BPO) antibodies. I. Biochemical and biophysical properties of anti-BPO-IgG obtained by affinity and subsequent ion-exchange chromatography.

Anti-BPO antibodies were purified by means of affinity chromatography using AH-Sepharose 4B coated with covalently bound BPO groups. Specific elution was achieved by the hapten analogue BPO-epsilon-aminocaproic acid (BPO-EACA); desorption of the remaining antibody was performed thereafter by 0.1 M acetic acid. The resulting antibody fractions--hapten-eluted antibody (H-Ab) and acid eluted antibody (A-Ab), respectively--were further separated by ion-exchange chromatography which led to the appearance of 3 subfractions in the case of H-Ab (H1, H2, H3) and 2 subfractions in the case of A-Ab (A1 and A2). In liquid isoelectrofocusing an inhomogeneous pattern resulted. The bulk of antibodies focused between pH 6.5 and 7.0. The average avidity of H-Ab was found to be higher than that of A-Ab suggesting that avidity may influence the elution pattern in affinity chromatography. The hydrophobic influence of the "spacer" and/or interactions of antibodies directed against the hydrophobic regions of the BPO group may explain why a considerable part of the antibodies could be recovered from the immunosorbent only by acid elution.     

Quantitative elution studies in experimental immune complex and nephrotoxic nephritis.

Optimal conditions have been determined for elution of antiglomerular basement-membrane antibodies and antigen-antibody complexes from nephritic kidneys, obtained from rabbits with nephrotoxic nephritis and various forms of BSA-induced immune complex disease. Elution from kidney homogenates was performed with acid and alkaline buffers, solutions of chaotropes, urea, sodium and magnesium chloride and other agents. Functional activity of antibodies exposed to elution procedures was tested by immunofluorescence, or by a modified Farr's technique. Antibodies of progressively greater binding capacity were eluted by a stepwise acid gradient (pH 3-2--2-8) using low or high ionic strength glycine--HCl buffer. Antigen-antibody complexes were best eluted using 3 M KBr (pH 9) using several extractive steps. A stepwise alkaline gradient (pH 10-5--11-1 using 0-1 M glycine-NaOH buffer) or 8 M urea were found to be satisfactory alternative methods of eluting immune complexes. Elution procedures were best carried out in the cold in all circumstances. Other eluting agents were found to be less successful or less practical.     

ABO血型新生儿溶血病患儿红细胞致敏抗体热放散效果与红细胞量的关系

目的 比较不同量的患儿压积红细胞进行热放散的放散效果差异,进而研究达到最强放散效果的压积红细胞最适使用量.方法 以14例疑似新生儿溶血病(HDN)患儿的血标本为研究对象,每例标本分别吸取100μL、200μL、300μL、500μL、1mL的患儿压积红细胞进行放散试验,采用微柱凝胶法检测放散后抗体,比较不同量的压积红细胞放散效果的差异.结果 14例疑似HDN患儿中,确诊为HDN 11例.11例标本随着压积红细胞量增加,放散抗体凝集强度均增加,到500μl增到最大,1mL与500μL凝集强度相同.其中8例标本(72.7%),5个梯度压积红细胞均可放散出抗体;3例标本(27.3%),红细胞量200μL以上才可放散出抗体.结论 不同量的患儿压积红细胞进行热放散的放散效果不同,随着红细胞量增加,放散抗体凝集强度增加,红细胞量过少可能导致放散试验假阴性.     

Unexpected interaction of some anti-TNP hybridoma antibodies with Superose HPLC gel filtration resins.

Five different hybridoma antibodies (the isotypes IgG1, IgG2a and IgG2b), reactive with TNP, showed increased elution times when gel filtered on a Superose-12 HPLC column corresponding to apparent molecular weights ranging from 54 kDa to 120 kDa compared to the normal of 150 kDa. One of the antibodies (C1901-B4) was studied in detail showing that the unusual gel filtration behaviour was localized to the Fab part of the molecule. SDS-PAGE analysis showed that the intact antibodies had normal molecular weights. Gel filtration on a Toyosoda G-3000SW HPLC column and Sephadex G-150 as well as Sepharose 6B generally showed normal elution times. These results support the hypothesis that the retardation on the Superose gel is probably due to aromatic interactions between amino acid residues supposedly exposed in the hypervariable region (i.e., the antibody combining site) of the antibody, and the gel matrix which is rich in ether O-atoms created during the manufacturing process. If this hypothesis is correct one might expect such interactions between Superose resins and antibodies of many different specificities in which aromatic amino acids are exposed in the combining sites.     

Enzyme immunoassay analysis of antibody specificities present in the circulating immune complexes of selected pathological sera

Using immobilized anti-C3 antibody and an enzyme immunoassay, sera from 26 patients (eight with systemic lupus erythematosus (SLE), four with Hashimoto's thyroiditis, eight haemophiliacs and six with post-hepatitis cirrhosis) containing high levels of circulating immune complexes (IC) were selected. The IC were precipitated with 2.5% polyethylene glycol, washed, treated with acid buffer, neutralized and tested using an enzyme immunoassay in parallel with the original sera for antibody activity against a panel of antigens: human myosin and thyroglobulin, mouse actin and tubulin, calf thymus DNA and trinitrophenyl coupled to bovine serum albumin (TNP/BSA). It was found that all the isolated IC may contain IgG, IgA and IgM antibodies reacting with actin tubulin and TNP/BSA and also, depending upon the disease, antibodies reacting with some of the other antigens of the panel. By comparison to the antibodies present in the original sera, higher titers of antibodies were found in the isolated IC while some antibody specificities not detected in a given serum were occasionally noted in the isolated IC. The antibodies present in the IC seem to possess characteristics similar to those of polyreactive human natural autoantibodies. It is concluded that natural autoantibodies participate actively in the formation of IC found in pathological sera.     

Separation and isolation of lymphocyte subpopulations of different affinity for the antigen

In order to separate, isolate, and determine the number and distribution of the subpopulations of lymphocytes of diverse affinities that are present in an immune response toward a single hapten, anti-trinitrophenyl (TNP) lymphocytes from immunized animals were purified by cell chromatography. Non-adherent spleen cells were passed through a column consisting of TNP-substituted polyacrylamide beads. The retained cells were eluted by applying a linear concentration gradient of TNP-lysine. Elution profiles having a limited number of peaks were obtained in all cases. The avidity of the cells in each fraction was measured by inhibition of formation of immune rosettes by free hapten. Results showed that each peak was located along the gradient according to its affinity since there was a direct correlation between the affinity and the concentration of hapten needed for the elution. The cells in each peak appeared to belong to a homogeneous subpopulation as shown by the slope of the curves obtained in the determination of avidity, suggesting that each peak corresponded to one expanded clone.     

Spectrotypic analysis of antibodies to acetylcholine receptors in experimental autoimmune myasthenia gravis

We have studied the isoelectric focusing pattern of antibodies expressed in rats with experimental autoimmune myasthenia gravis (EAMG) induced by immunization with acetylcholine receptors (AChR) purified from Torpedo californica. Sera or tissue eluates were obtained at intervals in the course of disease and subjected to isoelectric focusing. Subsequently, the focused antibodies were detected by autoradiography of gels labelled with 125I-alpha-bungarotoxin conjugated AChR. Reverse electrofocusing was used to separate complexes of antibody and AChR formed in vivo, thereby allowing detection of the full spectrotype (banding pattern). As little as 1.1 X 10(-12) moles of monoclonal antibodies (MoAbs) to AChR yielded distinct bands of radiolabelled antigen binding by this technique. The anti-AChR MoAbs studied showed a multitude of bands localized in neutral to alkaline position. The clonotypes expressed in late post-immunization sera were compared to early sera. The spectrotypes of immunized Lewis and Brown Norway rats were not identical. In early sera most of the isoelectric focusing bands were specific for T. californica AChR, whereas in late sera further expansion of the repertoire produced bands that reacted with rat muscle AChR as well. The focused bands that bound rat AChR also bound T. californica AChR. The anti-AChR antibodies eluted from muscles of rats with EAMG showed similar binding patterns to anti-receptor antibodies in rats' sera. These results indicate that the antibody specificities detected in serum are the same specificities which are effective in binding to muscle AChR in vivo. Minor specificities of serum anti-receptor antibodies are not disproportionally represented in the antibodies actually bound at the neuromuscular junction in EAMG.