Fc receptors of endothelial cells of cardiac valves: comparison of IgG Fc binding activity of these receptors and of Fc receptors of group A streptococci

Normal human and rabbit sera, as well as IgG isolated from them, have proved to be capable of reacting with the cells of the valve endothelium of the human and bovine heart. As shown in this study, these reactions are linked with the presence of Fc receptors on the epithelial cells. This is confirmed by the positive reactions of the endothelial cells with the Fc fragments of IgG, as well as with pure antibodies to egg albumin and to group A streptococcal polysaccharide and their complexes. As revealed in this study, Fc receptors on endothelial cells and staphylococcal Fc receptors bind with the definite fraction of normal human serum IgG with, probably, more pronounced cytophil properties. This fraction is not linked with IgG subclasses. The suggestion may be made that the presence of IgG Fc binding activity in group A streptococci, coinciding with the binding activity of Fc receptors in some cells of the human body, is probably of importance for pathogenic streptococci, facilitating their successful invasion.     

Prevention of Bacteriophage Adsorption to Staphylococcus aureus by Immunoglobulin G

Normal human and rabbit sera when incubated with Staphylococcus aureus inhibit the adsorption of bacteriophages. The bacteriophage adsorption was also inhibited by separated normal immunoglobulin M (IgM), F(ab')(2), and Fab-fragments of IgG. No inhibition was obtained with myeloma IgG or Fc-fragments of normal human and rabbit IgG. The results indicate that the serum inhibition of bacteriophage adsorption to S. aureus is not due to a binding of IgG to protein A on the surface of S. aureus.     

Bindings of plasma proteins to streptococci of serological group L with special reference to their immunoglobulin G Fc-receptor activity

Of 33 streptococcal cultures belonging to serological group L, all bound human immunoglobulin (Ig) G, fibrinogen, and fibronectin; 32 bound bovine IgG; 31 bound alpha 2-macroglobulin; 5 bound albumin; and none bound either haptoglobin or IgA. The binding sites for IgG could be isolated from the L streptococci by trypsinization and purified by affinity chromatography on human IgG-Sepharose. The purified Fc receptors reacted with IgG subclasses 1, 2, 3, 4 of humans, 1 and 2 of bovines, ovines, and caprines as well as a, b, c, and T of equines. They had a molecular mass of approximately 49,000 Da. Thus, the Fc receptors from L streptococci corresponded to type III Fc receptors of Streptococcus dysgalactiae.     

Role of group A streptococcal IgG Fc-receptor in induction of anti-IgG by immunization in the rabbit

Previous work has demonstrated that streptococcal IgG Fc-receptors (FcR) may trigger production of anti-IgG after immunization of rabbits with group A streptococci. This effect seemed dependent on in vitro binding of IgG, derived from the growth medium, to the vaccine strains. In the experiments presented here, IgG was eluted from streptococcal strains to be used for immunization of rabbits by 1 M KSCN and washing, a treatment which did not affect the capacity of the strains to bind newly added IgG. Using two IgG FcR-positive group A streptococcal strains (M-types 1 and 22) for intravenous immunization, anti-IgG was found in the sera of 26 out of 28 rabbits, examined 8 weeks after immunization. In contrast, anti-IgG was not induced in 16 rabbits receiving either group A, type T27 or group B, type Ia streptococci both of which lack surface FcR activity. Finally, immunization with purified streptococcal IgG FcR (0.35 mg, given subcutaneously combined with Freund's complete adjuvant and two weeks later intraconjunctivally without adjuvant) also induced anti-IgG. In all rabbits, anti-human rather than anti-rabbit IgG was detected. It is proposed that in vivo interaction between the bacterial FcR and rabbit IgG, resulting in conformation changes in IgG, is a prerequisite for the induction of anti-IgG. Thus, streptococcal triggering of anti-IgG, ascribable to IgG Fc-receptor activity and not requiring presence of foreign IgG, has been demonstrated in the rabbit.     

Role of group A streptococcal IgG Fc-receptor in induction of anti-IgG by immunization in the rabbit

Abstract Previous work has demonstrated that streptococcal IgG Fc-receptors (FcR) may trigger production of anti-IgG after immunization of rabbits with group A streptococci. This effect seemed dependent on in vitro binding of IgG, derived from the growth medium, to the vaccine strains. In the experiments presented here, IgG was eluted from streptococcal strains to be used for immunization of rabbits by 1 M KSCN and washing, a treatment which did not affect the capacity of the strains to bind newly added IgG. Using two IgG FcR-positive group A streptococcal strains (M-types 1 and 22) for intravenous immunization, anti-IgG was found in the sera of 26 out of 28 rabbits, examined 8 weeks after immunization. In contrast, anti-IgG was not induced in 16 rabbits receiving either group A, type T27 or group B, type Ia streptococci both of which lack surface FcR activity. Finally, immunization with purified streptococcal IgG FcR (0.35 mg, given subcutaneously combined with Freund's complete adjuvant and two weeks later intraconjunctivally without adjuvant) also induced anti-IgG. In all rabbits, anti-human rather than anti-rabbit IgG was detected. It is proposed that in vivo interaction between the bacterial FcR and rabbit IgG, resulting in conformation changes in IgG, is a prerequisite for the induction of anti-IgG. Thus, streptococcal triggering of anti-IgG, ascribable to IgG Fc-receptor activity and not requiring presence of foreign IgG, has been demonstrated in the rabbit.     

Evidence for functional heterogeneity in IgG Fc-binding proteins associated with group A streptococci

A number of group A streptococcal isolates have been compared for their nonimmune reactivity with each human IgG subclass, and rabbit, pig, or horse IgG. The results obtained demonstrate considerable heterogeneity in the expression of type II IgG-binding proteins among and within group A isolates. Extraction and analysis of type II IgG-binding proteins from selected strains demonstrate the existence of five functionally distinct IgG-binding proteins. The type IIo IgG binding protein displayed the greatest range of reactivities, binding to all four human IgG subclasses, and rabbit, pig, and horse IgG. A variant of this protein, designated type II'o, bound all four human subclasses and rabbit IgG, but failed to react with pig or horse IgG. A type IIa protein was recovered from certain group A strains which bound human IgG1, IgG2, IgG4, as well as reacting with rabbit, pig, and horse IgG. A functionally related type IIc activity that displayed all of the reactivities of the type IIa protein but did not bind with human IgG2 was also identified. The final functional form of group A IgG-binding protein, the type IIb protein, bound exclusively to human IgG3. Comparison of these functionally different type II IgG-binding proteins demonstrated no simple structure-function relationship. These studies underscore the heterogeneity of type II Ig-binding proteins expressed by different group A streptococci and document that a single strain can change its pattern of expression of type II IgG-binding protein both quantitatively and qualitatively.     

F(ab')2 reagents are not required if goat, rather than rabbit, antibodies are used to detect human surface immunoglobulin.

The present report provides evidence that whole goat anti-human immunoglobulin, unlike similar reagents produced in the rabbit, binds both to the same number of and the same individual cells as the F(ab')2 fragments of rabbit or goat anti-human immunoglobulin. These results suggest that goat IgG has a lower affinity for the Fc receptors of human lymphocytes and monocytes than rabbit IgG. Because of this property, whole goat antibodies against human immunoglobulin can be used as simple, convenient relatively inexpensive reagents for the routine detection of immunoglobulin on cell surfaces by immunofluorescence microscopy. The preparation of F(ab')2 fragments of anti-immunoglobulin, which are necessary when rabbit antibodies are used, does not appear to -e required if goat antibodies can be empolyed. This observation has multiple practival applications in cellular immunology.     

Pertussis toxin and cross-reactive antigens in dynamics of Bordetella pertussis cultivation

Cultures of Bordetella pertussis from phases of exponential growth, retarded growth and from stationary phase were obtained during periodic dynamic cultivation. Preparations for intravenous immunization of rabbits were made from these cultures. Levels of IgG to pertussis toxin, cell walls preparations from 12 bacterial species, 4 organo-specific antigens, and 7 organospecific human antigens were measured in obtained sera. It was shown that higher levels of IgG to pertussis toxin were found in sera of rabbits immunized with cultures from exponential growth phase whereas decrease of this level in 8 times was observed in sera of rabbits immunized with cultures from retarded growth phase or end of stationary phase. After immunization with culture from exponential growth phase increase of IgG levels to cross-reactive antigens was not observed compared to levels of these antibodies in control sera obtained before immunization. After immunization with cultures from retarded growth phase or end of stationary phase increase of IgG levels to preparations of cell walls of Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, to denaturated DNA, elastin, and renal and liver microsomal fractions was detected compared to control sera. Described data can substantiate usefulness of obtaining the most specific diagnostic sera and test-systems using cultures of B. pertussis from the phase of exponential growth.     

Heterogenetic antigens of gram-positive bacteria

Chorpenning, Frank W. (The Ohio State University, Columbus), and Matthew C. Dodd. Heterogenetic antigens of gram-positive bacteria. J. Bacteriol. 91:1440-1445. 1966.-Soluble antigens obtained by various methods from gram-positive bacteria were used to modify erythrocytes whose hemagglutinating reactions with immune rabbit sera and normal human sera were then studied. Antigens from all gram-positive organisms studied except corynbacteria altered red cells, causing them to react with specific bacterial antisera and with normal human sera; however, cross-absorption and inhibition tests indicated that at least three different specificites were involved. One of these antigens seemed to be similar to Rantz's streptococcal NSS, which is shared with Staphylococcus aureus and Bacillus spp., and is therefore heterogenetic. Another was found in streptococci but was apparently not present in S. aureus and Bacillus spp. A third antigen, also heterogenetic, appeared to be shared by several species of Bacillus and by S. aureus, but not by streptococci or any gram-negative bacteria. The third antigen was heat-stable at pH 8.0, and appeared to be essentially polysaccharide in nature. Normal human sera varied in their content of antibodies which reacted with erythrocytes modified by extracts from gram-positive bacteria. Whereas some sera reacted very broadly with red cells modified by extracts of practically any gram-positive organism, other sera agglutinated only cells which had been modified by streptococcal antigen.     

应用兔抗大熊猫免疫球蛋白G血清探讨大熊猫的分类地位

从大熊猫血清中纯化出免疫球蛋白(IgG),以此作为抗原免疫家兔,获得兔抗大熊猫IgG血清。以黑熊、小熊猫、狗、猫等动物血清为抗原,兔抗大熊猫IgG 血清为抗体．进行了免疫扩散和微量免疫电泳实验。 实验结果表明,收集的食肉目动物：黑熊、小熊猫、狗、猫的血清都可与兔抗大熊猫GIg血清进行沉淀反应,其中尤以黑熊的反应最强且与大熊猫的反应沉淀线完全融合;小熊猫、狗、猫反应较弱且融入大熊猫反应沉淀线后形成树板状。从此看出大熊猫lgG 与黑熊的IgG最相似,从亲缘关系上讲,二者更为接近,大熊猫反应属熊科。     

Prevention of Staphylococcal Bacteriophage Activity by Antigen A Precipitins in Human Sera

Antigen A precipitins in human sera prevented plaque formation and propagation of staphylococcal bacteriophages. Over 20% of total IgG was removed from human sera by absorption with staphylococci containing antigen A. The specific precipitating antibody in rabbit antisera formed lines of idenity with antigen A precipitins in lower dilutions of human sera but formed lines of nonidenity with antigen A precipitins in higher dilutions of the same sera, suggesting both specific and nonspecific antigen A precipitins in human sera. The specific and nonspecific antigen A precipitins in human sera may prevent the in vivo activity of staphylococcal bacteriophages which have been demonstrated previously in animals whose sera do not contain either specific or nonspecific antigen A precipitins.     

Electron microscopic study of the location of the Fc-reacting factor on group A streptococci

The presence of the Fc-reacting factor was demonstrated on four out of five different group A Streptococcus strains using ferritin-labelled immunoglobulin G. A comparison of the results obtained by this electron microscopic technique with Fc-reacting factor detection results obtained with hydrochloric acid extracts of cells in passive haemagglutination on sensitized red cells, showed that not only hydrochloric acid extractable but also non-extractable Fc-reacting factor can be present on the group A Streptococcus cell. Out of several IgGs tested, only rabbit and swine IgGs bound to Fc receptors of group A Streptococcus walls. The Fc-reacting factor is ultrastructurally localized on the tips of the filamentous protrusions forming the outermost layer of the Streptococcus wall. The involvement of the Fc portion of IgG in the reaction was demonstrated by a positively reacting sandwich arrangement in which Streptococcus cells were incubated with rabbit antiferritin before being treated with ferritin.     

Purification and some properties of streptococcal protein G, a novel IgG-binding reagent

Protein G, a bacterial cell wall protein with affinity for immunoglobulin G (IgG), has been isolated from a human group G streptococcal strain (G148). Bacterial surface proteins were solubilized by enzymatic digestion with papain. Protein G was isolated by sequential use of ion-exchange chromatography on DEAE-cellulose, gel filtration on Sephadex G-100, and affinity chromatography on Sepharose 4B-coupled IgG. The presence of protein G in various pools and fractions during the isolation was followed by their ability to inhibit the binding of radio-labeled IgG to G148 bacteria. A highly purified protein G was obtained. On polyacrylamide gel electrophoresis in sodium dodecyl sulfate, the apparent m.w. was 30,000, and on agarose gel electrophoresis the purified protein gave rise to a single band in the alpha 1-region. Protein G was found to bind all human IgG subclasses and also rabbit, mouse, and goat IgG. On the IgG molecule, the Fc part appears mainly responsible for the interaction with protein G, although a low degree interaction was also recorded for Fab fragments. IgM, IgA, and IgD, however, showed no binding to protein G. This novel IgG-binding reagent promises to be of theoretical and practical interest in immunologic research.     

Reaction Pattern in Vertebrate Cells (RiV): May the anti‐RiV ELISA Detect a Pathologic Cell Proliferation? (First Results)

RiV is mainly represented by characteristic exosome‐like particles with a diameter of 30 to 70 nm. RiV particle preparations (RiV‐PP) contain identified proteins. In the present paper, the authors started an evaluation of the hypothesis, that RiV‐reactive antibodies, detected in patient sera by an indirect ELISA, may be used for the diagnosis of pathologic cell proliferations. On the basis of the frequency distribution curve of about 500 blood donor sera, cut‐off values for RiV‐reactive IgG and IgM antibodies could be defined. Additionally it was found that 1.6 % of blood donor sera reacted strongly with an RiV‐PP (of calf kidney cells) for IgG antibodies. 29 % of cancer patient sera (n = 48), 17 % of 53 patients with endoprothetics and with lung disorders, 44.3 % of 115 patient sera of a doctor's practice and 28 % of 97 sera of 10 to 11 years old schoolchildren were positive in the anti‐RiV ELISA with IgG antibodies. About half of the selected group of schoolchildren contained different autoantibodies and some of these children displayed already insulin dependent diabetes mellitus (as shown by others). A correlation of our ELISA results with the other autoimmune antibody results was not found. Using RiV‐PP as an antigen complex, isolated from calf kidney cell cultures or from human FL cell cultures and HeLa cell cultures, results with small differences between human and animal RiV origin were obtained. Using the human RiV, the number of positive sera was not significantly lower. Generally, the anti‐RiV ELISA, using RiV‐PP from human cell cultures, detect autoantibodies against RiV‐specific proteins. This assay may detect, but not diagnose pathologic cell proliferation. The possibilities of RiV ELISA for diagnostics of defined autoimmune diseases, as well as further studies and the more meaningful RiV immunoblot are discussed.     

Heat elution chromatography of immunoglobulins

A tremendous increase has taken place over the last decades in the biochemical and clinical use of antibodies. Unfortunately, the constantly growing demand has not been matched by a corresponding easy access to pure immunoglobulin, as purification procedures tend to be either laborious, expensive, or inefficient. We present a new and simplified method to obtain pure antibody based on the special thermal properties of the streptococcal M proteins, a family of cell-surface exposed coiled-coil molecules which bind different sets of host plasma proteins. The coiled-coil structure is already destabilized at low temperatures and the M proteins unfold reversibly, usually below 40 degrees C. We demonstrate the use of this property to purify immunoglobulin G from rabbit serum with protein H from the AP1 strain of Streptococcus pyogenes. Recombinant protein H is linked to nickel-agarose via a C-terminal histidine tag. After mixing with rabbit serum and washing at room temperature, pure IgG can be eluted from the gel with a moderately heated buffer. In this case, protein H has been used to purify rabbit IgG, but the principle should be applicable to other M protein-ligand pairs.     

Rapid detection of porcine circovirus type 2 using a TaqMan-based real-time PCR

Background

In assays for anti-hepatitis E virus (HEV) immunoglobulin M (IgM), large volumes of the patient's sera cannot be easily obtained for use as a positive control. In this study, we investigated an alternative chemical method in which rabbit anti-HEV IgG was conjugated with human IgM and was used as a positive control in the anti-HEV IgM assay. Rabbit anti-HEV IgG was isolated from immune sera by chromatography on protein A-Sepharose and was conjugated with human IgM by using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as a crosslinker.

Results

The specific anti-HEV IgG antibody titer was 100,000 times that of the negative control, i.e., prebleed rabbit serum. The results of anti-HEV IgM enzyme-linked immunosobent assay showed that the antibody conjugate was similar to anti-HEV IgM antibodies produced in humans. The results of a stability experiment showed that the antibody conjugate was stable for use in external quality assessment or internal quality control trials.

Conclusions

We concluded that the chemically conjugated rabbit-human antibody could be used instead of the traditional serum control as a positive control in the anti-HEV IgM assay.     

Immunochemical properties of immunoglobulin G conjugated with dextran

Antigen-binding activity and effector functions of immunoglobulin G from horse and rabbit sera have been investigated, using hemagglutination, kinetic immune lysis, immune lysis in microplates and rosette-forming test with peritoneal mononuclear cells of mice, after their conjugation with dextran, MW 35-50 kD. The formation of conjugates of two types has been demonstrated: protein-dextran and protein-dextran-protein. It has been revealed that protein-dextran-protein conjugates have high specific antigen-binding activity, as compared to native IgG from rabbit sera specific for SRBC, while interactions with the complement system and Fc receptors is depressed.     

Humoral immunity aspects of meningococcal infection. I. A method of performing and the characteristics of the immune bacteriolysis reaction]

Immune bacteriolysis test with meningococcus, group A, was used for the purpose of serum antibody study. Meningococcus cultures with a bright orange fluorescence of the colonies in oblique illumination (the I type) proved to possess the greatest lysability. Guinea pig serum sorbed with meningococcus suspension was found to be the best source of the complement. Sera obtained after 1 to 3 days of rabbit immunization, containing mostly IgM antibodies, had the greatest bactericidal capacity. Only those fractions which contained IgM possessed bactericidal activity in the hyperimmune rabbit sera with a high IgG antibody concentration. No lytic activity was displayed against meningococcus by unfractionated hyperimmune sera.     

A physicochemical study of protein G, a molecule with unique immunoglobulin G-binding properties

Protein G, an IgG-binding molecule, was prepared from the cell walls of a group G streptococcal strain, G-148. The protein could be extracted from the cells by papain digestion and purified by the sequential use of ion-exchange chromatography on DEAE-Sephadex, affinity chromatography on Sepharose-coupled human IgG, and gel chromatography on Sephadex G-200. Two protein bands with similar molecular weight, 34,000 and 36,000, were obtained when analyzing the pure protein G on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The yield using this purification scheme was 27% of the protein G solubilized from the cells or 70 micrograms/ml packed bacteria. The Stokes radius and frictional ratio of protein G were determined to 3.53 nm and 1.64, respectively, suggesting an elongated fibrous molecule. The protein did not contain any intrachain disulfide bonds. The amino acid composition of protein G was determined and was found to be different from that of protein A, the well known staphylococcal IgG-binding protein. The equilibrium constants of the reactions between protein G and human, rabbit, mouse, and goat polyclonal IgG, determined by Scatchard plots, ranged between 1 X 10(10) and 7 X 10(10), for rat polyclonal IgG 1.4 X 10(9), and human monoclonal IgG1, IgG2, IgG3, and IgG4 between 2 X 10(9) and 6 X 10(9). These affinity constants were always greater than the corresponding values for protein A. The binding between protein G and various polyclonal and monoclonal IgG was pH dependent between 2.8 and 10, strongest at pH 4 and 5, and weakest at pH 10.     

Biological screening of monoclonal antibodies

A method was developed to screen hybridomas secreting immunoglobulin to cell surface receptors by observing the ability of antibodies to inhibit cell attachment and survival. The model used to develop the screening procedure involved mouse hybridomas secreting monoclonal IgG to human epidermal growth factor (EGF) receptors. Conditioned medium from these hybridomas inhibited the attachment and subsequent growth of human foreskin fibroblasts unless excess EGF was added to the cultures. This procedure allows for the selection of hybridomas producing increased levels of immunoglobulin.