Cross-reactivity of human and a putative pig IgD. pig IgD-like molecules as serum and lymphocyte components

Proteins of pig serum and splenocytes which were isolated on immobilized guinea pig antibodies against human IgD were characterized by SDS-PAGE. In both cases the main isolated components possessed several properties nearly identical with those of human IgD: molar mass of the components and their chains, and susceptibility of the heavy chains, light chains, the chymotryptic peptide maps of the chains, and susceptibility of the heavy chains, the chymotryptic peptide maps of the chains, and susceptibility of the heavy chains in the native molecule to trypsin digestion. These IgD-like components not adsorbed on immobilized normal guinea-pig IgG. We suggest that the components of pig serum and splenocytes cross-reacting with highly specific antibodies against human IgD represent candidates for pig IgD. The percentage of the IgD-like molecules on the surface of pig splenocytes labeled with the antibody against human IgD was similar to the percentage of splenocytes bearing all immunoglobulins. Therefore, we suggest that IgD-like molecules were occurring on the surface of cells mostly together with molecules of another immunoglobulin class.     

In vivo cross-linking of protein disulfide isomerase to immunoglobulins

To test the proposed role of protein disulfide isomerase in the synthesis of immunoglobulins (Ig), intact lymphocytes were treated with a thiol-cleavable, bifunctional cross-linking agent and lysed, and the lysates were immunoprecipitated with antibodies to either Ig or enzyme. When the immunoprecipitates were analyzed on polyacrylamide-sodium dodecyl sulfate gels, protein disulfide isomerase was found to be cross-linked to immunoglobulins. The extent of cross-linking was dependent upon the concentration of cross-linker added and the class of Ig. For IgMs and high concentrations of cross-linker, approximately one molecule of Ig was coupled per two molecules of enzyme. For IgGs, the extent of cross-linking was less. Finally, depletion of the intracellularly reduced glutathione by diamide was found to also result in the linkage of protein disulfide isomerase to IgM. These results therefore support the hypothesis that protein disulfide isomerase functions in the in vivo synthesis of immunoglobulins.     

Reversible cross-linking of crystalline bacterial surface layer glycoproteins through their glycan chains

After periodate oxidation and incubation with dithiodipropionic acid dihydrazide cross-linking of the crystalline surface layer (S-layer) glycoproteins of Clostridium thermohydrosulfuricum L111-69 and Bacillus alvei CCM 2051 was achieved specifically through the glycan chains. The cross-linked S-layers were used for the immobilization of chemically synthesized, spacer-linked, tumour-associated T-disaccharide [Gal(13)GalNAc]. Electron microscopical evaluation of the resulting conjugates showed densely packed, multilayered S-layer structures loaded with the immobilized ligand. After reductive cleavage of the disulphide bond of dithiodipropionic acid by dithiothreitol, monomeric haptenated S-layer conjugates could be obtained. Both the cross-linked and the monomeric type of conjugate might be useful for assessment of specific immune responses, which, in general, can be elicited by those artificial antigens. Correspondence to: P. Messner     

Immunofluorescent localization of pig complement component 3, regardless of the presence or absence of detectable immunoglobulins, in hyperacutely rejected heart xenografts

Summary Rabbit heart xenografts transplanted into the neck of newborn pigs were all hyperacutely rejected within two hours regardless of the presence or absence of detectable endogenous immunoglobulins (Ig). Cryostat tissue sections were prepared from the rejected rabbit hearts and incubated with sheep polyclonal antibodies against pig complement component 3 (C₃), pig IgG and pig IgM. Specific immunoreaction was visualized by fluorescein-conjugated antibodies to sheep IgG. C₃ was localized mainly on the surfaces of vascular endothelial as well as myocardial cells, and the localization was not dependent upon the presence of pig immunoglobulins within the same tissue. Both pig IgG and IgM were detected only in the heart xenografts transplanted into suckled pigs, whereas no trace of immunoglobulin was found in those transplanted into circulating antibody-free presuckled pigs. Treatment with cobra venom factor (which inhibits complement activity) prior to transplantation prolonged xenograft survival and completely abolished C₃ immunostaining. The results provide new evidence at the histochemical level that the alternative pathway of complement is involved in hyperacute xenograft rejection of the species combination (rabbit to pig) used in this study.     

Evidence for the association between two myosin heads in rigor acto-smooth muscle heavy meromyosin

The rigor complexes that formed between rabbit skeletal muscle F-actin and chicken gizzard heavy meromyosin (HMM), in which the heavy chains had been cleaved with trypsin into 24K, 50K, and 68K fragments, were examined by using the zero-length chemical cross-linker 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). Two cross-linked products of approximate Mr 115K and 60K were generated. These products were not obtained by EDC treatment of HMM in the absence of F-actin. The HMM fragments that participated in cross-linking were identified by fluorescent labeling and amino acid composition studies. The 115K peptide was determined to be a covalently cross-linked complex that formed between actin and the COOH-terminal 68K fragment of the HMM heavy chain. Our results are in agreement with a previous study which proposed that the site of cross-linking between HMM and F-actin resides within the COOH-terminal 22K fragment of the myosin subfragment 1 heavy chain [Marianne-Pépin, T., Mornet, D., Bertrand, R., Labbé, J.-P., & Kassab, R. (1985) Biochemistry 24, 3024-3029]. The 60K peptide, however, was not a product of cross-linking between HMM and F-actin. On the basis of its amino acid composition, we concluded that this 60K peptide was a cross-linked dimer of the NH2-terminal 24K fragments of the HMM heavy chain. The cross-linking of acto-gizzard HMM significantly increased the Mg-ATPase activity of gizzard HMM without any observable phosphorylation of the regulatory (20K) light chains.(ABSTRACT TRUNCATED AT 250 WORDS)     

Null cells in the mouse possess membrane immunoglobulins.

Null cells lacking typical T and B cell surface markers were isolated from the spleens of congenitally athymic mice by using either nylon wool or Sepharose macrobeads conjugated with rabbit antibody to mouse IgM to remove B lymphocytes. Although these null cells were negative for surface immunoglobulin by the criterion of immunofluorescence by using rabbit antisera to mouse heavy or light immunoglobulin chains, surface immunoglobulins were readily demonstrable by two alternative and independent techniques. First, by using chicken antibody to the (Fab')2 fragment of mouse IgG, nearly all null cells were positive for immunofluorescence. Second, immunoglobulins could be detected in lysates of null cells radioiodinated by the lactoperoxidase-catalyzed reaction. Analysis of the surface immunoglobulins of null cells by radioimmunoassay and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate suggested that they are 1) qualitatively similar to those of B cells and 2) present in amounts between 10 and 30% of those of B cells.     

Molecular stability of chicken and rabbit immunoglobulin G.

Molecular stability of chicken egg yolk immunoglobulin G (IgY) and that of rabbit IgG were compared by measuring antibody activities and conformational changes. Stability of rabbit IgG to acid denaturation was much higher than that of IgY. Conformation of the IgY molecule was readily changed in acidic conditions, resulting in a rapid loss of antibody activity. Much less stable natures of IgY to heat-treatment and guanidine-HCl denaturation than rabbit IgG were also observed. Differences in the structure between the two immunoglobulins that might participate in their different stability were inferred from their amino acid sequence data. Importance of the intramolecular disulfide linkage in the rabbit light chain and some other structural differences were suggested.     

The N-terminal sequence of the heavy chain of rabbit immunoglobulin IgG

The absence of an N-terminal amino acid with a free alpha-amino group from the heavy chain of rabbit immunoglobulin IgG has been confirmed and no evidence could be found of a blocking formyl, acetyl or propionyl group. The N-terminal amino acid appears to be pyrrolid-2-one-5-carboxylic acid (PCA) in all molecules. A mixed amino acid sequence follows in the approximate proportions: PCA-Ser-Val-Glu-Glu-Ser-Gly-Gly-Arg, 50%; PCA-Ser-Leu-Glu, 20%; PCA-Glu(NH(2)), 20%. The heavy chains of a purified antibody, namely anti-(human serum albumin), and of immunoglobulin IgG from a rabbit homozygous at the allotypic loci both showed a similar mixed N-terminal sequence.     

Sequence comparison of human plasma alpha1-acid glycoprotein and the immunoglobulins

The amino acid sequence of human plasma alpha1-acid glycoprotein, upon comparison with the sequences of other blood proteins, was shown to possess significant similarity with the immunoglobulins. Employing direct and corrected sequence identity, the average mutation value and two different computer comparisons for the evaluation of sequence similarity, the following two regions of this alpha-globulin, which account for approximately half of the total amino acid sequence of the protein, were found to possess sequence similarity with the immunoglobulins. a) The region from residues 77 through 125 proved to be related to the variable region of several human H and L chains, and b) the region from residues 136 through 166 was found to be related not only to the constant region of a human and a mouse L chain but also to the third and fourth constant region of a rabbit and a human H chain, respectively. These results suggest that alpha1-acid glycoprotein is probably related to the immunoglobulins and further suggest that it possibly diverged from the immunoglobulin evolutionary tree prior to the formation of the primitive L chain.     

Anti-Ro autoantibody with cross-reactive binding to the heavy chain of immunoglobulin G.

Autoantibodies directed at the intracellular Ro ribonucleoprotein complex are found in the serum of patients with systemic lupus erythematosus (SLE) and related autoimmune diseases. The antigenic stimulus for the induction of these autoantibodies is unknown, although we have previously demonstrated that the Ro protein and immunoglobulin G (IgG) share immunologic determinants bound by anti-Ro antibodies. The present study further defines the fine specificity of this cross-reactive binding. Using both patient autoanti-Ro antibodies and antigen-induced rabbit anti-Ro serum, the binding specificity for IgG was located to the heavy chains of IgG outside the Fc domain. F(ab')2 fragments of IgG were observed to inhibit specific Ro binding by either human or antigen-induced rabbit sera, while Fc fragments of IgG failed to inhibit Ro binding. Anti-Ro sera were found to bind the heavy chains of IgG in immunoblots, and the antibodies eluted from these heavy chains were capable of immunoprecipitating the Ro particle from human cell extracts. Not all patient sera with anti-Ro antibodies possessed IgG binding antibodies. Studies of cyanogen bromide digestion fragments of IgG implicate the hinge region of IgG as the region cross-reactive with the Ro protein. The nature of this cross-reactivity may be important in understanding the induction and/or perpetuation of the anti-Ro response in patients with autoimmune disease.     

Amino acid sequence of the N-terminal sixty-nine residues of heavy chain derived from a homogeneous rabbit antibody

The sequence of the N-terminal 69 residues of heavy chain from a homogeneous rabbit antibody to type III pneumococcal polysaccharide was determined. The sequence is similar to that found in heavy chains of normal pooled rabbit immunoglobulins of the same allotype Aa1. Two regions of the homogeneous heavy chain (residues 35-46 and 62-69) are very similar to corresponding regions of heavy chains from rabbit Aa2 immunoglobulin, as well as from mouse, guinea-pig and human immunoglobulins. In contrast, residues 47-62 appear to be variable. Comparison in this section with another homogeneous anti-pneumococcal antibody (Strosberg et al., 1972) of related specificity and of the same allotype indicates sequence variation in at least three positions. An antibody to group C streptococcal carbohydrate of allotype Aa2 (Fleischman, 1971) differs by five amino acids in the same region of the heavy chain. Sequence variability between these three antibodies does not occur in homologous positions within this variable section. Allotype-related sequences could not be identified in section 34-65.     

Coxsackievirus and adenovirus receptor (CAR) binds immunoglobulins.

The coxsackievirus and adenovirus receptor protein (CAR) serves as the cell surface receptor for group B coxsackieviruses and most adenoviruses, but the physiological function and ligand for this protein remain to be described. An affinity column was constructed with the recombinant extracellular domain of the CAR (rECAR) to isolate potential ligands by affinity chromatography. Immunoglobulins G and M were consistently isolated from human sera passed through the column, suggesting that the CAR may be an immunoglobulin-binding protein. Further investigation revealed that the affinity-purified immunoglobulins bound to rECAR-coated immunoassay plates, and the peroxidase-labeled rECAR bound the immunoglobulins on ligand-overlay blots. The peroxidase-labeled rECAR was incorporated into immunoprecipitates formed between the affinity-purified immunoglobulins and rabbit antibodies against human immunoglobulins, but not into immunoprecipitates formed between mouse IgG and rabbit antibodies against mouse IgG. The CAR present in HeLa cell lysates also bound to the affinity-purified immunoglobulins on Immobilon membranes, showing that the association is not limited to the recombinant protein. These results demonstrate that the CAR binds IgG and IgM present in serum, and reveal a direct interaction between the coxsackievirus and adenovirus receptor and the immune system.     

Binding of myosin cross-bridges to thin filaments of rabbit skeletal muscle.

Cross-linking of myosin subfragment 1 (S1) with a molar excess of actin in vitro reveals the presence of an actin-S1-actin complex. It is absolutely essential that actin be present in molar excess over S1 so that the decoration of F-actin with S1 be incomplete. However, the excess of actin may not be available in the overlap zone of sarcomeres of skeletal muscle. We therefore found it necessary to test for the presence of the actin-S1-actin complex in vivo. Myofibrils from rabbit skeletal muscle were reacted with zero-length cross-linker, the products were resolved by polyacrylamide gel electrophoresis and analyzed by Western blots using antibodies against actin and against heavy and light chains of myosin. The cross-linking produced the evidence of formation of actin-S1-actin complex.     

Structure and specificity of antibody molecules.

The structure of the Fab' fragment of a human myeloma protein (IgG1 (lambda) New) has been determined by X-ray crystallographic analysis to a nominal resolution of 0.2 nm. Each of the structure subunits corresponding to the variable and to the constant homology regions of the light and heavy polypeptide chains contains two irregular beta-sheets which are roughly parallel to each other and surround a tighly packed interior of hydrophobic side chains. The regions of the hypervariable sequences in the light and heavy chains occur in close spatial proximity at one end of the molecule, defining the active site of IgG New. The role of these hypervariable regions in defining the size and shape of the active site of different immunoglobulins is discussed on the basis of the three-dimensional model of Fab' New. Several ligands that bind to the active centre of IgG New have been used to obtain crystalline ligand-Fab' New complexes which were investigated by difference Fourier maps. These studies are analysed in terms of the biological function and specificity of antibodies.     

Fractionation of immunoglobulins by liquid-liquid partition chromatography in aqueous two-phase systems

In this paper we show that although immunoglobulins are easily precipitated in solutions containing polyethylene glycol (PEG), especially at pH's where the conformation of the proteins should be close to native, human and rabbit IgG can be solubilized in aqueous dextran/PEG two-phase systems containing glycine and sodium chloride at pH 7.0 and that human IgA and IgM can be solubilized in such systems if the pH is increased to 9.0. Liquid-liquid partition chromatography (LLPC) on Li-ParGel was used to separate immunoglobulins into subfractions. Human IgG, IgM, and IgA all gave three peaks in the system used. These results indicate the possibility of separating different classes of immunoglobulins with this method. Specific IgG antibodies isolated from a rabbit antiserum against human serum proteins gave only two peaks in the LLPC system while the total IgG population gave three, as did human IgG. Thus, partitioning of immunoglobulins seems to be related to antibody activity.     

Guinea pig peritoneal macrophages. Differential effects of lectins on interaction with IgG immunoglobulins

Guinea pig peritoneal macrophages have on their surface two receptors, one (Fcγ₁/γ₂R) binding both guinea pig IgG1 and IgG2 and the second (Fcγ₂R) binding only IgG2 immunoglobulins. We have previously shown that treatment of macrophages with neuraminidase or glycosylation inhibitors affects, in a different way, the binding of guinea pig IgG1, IgG2, and rabbit IgG. In the present study we have shown that pretreatment of guinea pig macrophages with lectins (Con A, WGA, and PNA) also has a different effect on the interaction of the cells with IgG. The lectins increased the binding of guinea pig IgG1, whereas rabbit IgG and guinea pig IgG2 were bound with a lower efficiency than in the case of control cells. Since sialic acid residues seem to modulate the activity of receptors and WGA interacts with sialylated oligosaccharides, we determined the IgG-binding characteristics for WGA-pretreated macrophages. We found that the increase in IgG1-binding ability was caused by an increase in the value of K_app, but the number of IgG-binding sites was lower than in the control cells. In the case of rabbit IgG and guinea pig IgG2 we observed a decrease of both the value of K_app and the number of IgG-binding sites. WGA did not interact directly with the Fcγ receptor. The results of our former papers and the different effects of lectins of various specificities described in this paper suggest different positions of Fcγ₁/γ₂ and Fcγ₂R in the plane of the plane of the macrophage membrane in respect to various membrane glycoconjugates. Interaction of IgG with macrophage Fcγ receptors depends in a different way on glycoconjugates on the surface of the macrophage. Our results suggest that changes in glycosylation of macrophage surface glycoconjugates may be used by the cell for regulating the binding activities of the macrophage Fcγ receptors.     

Allotypically related sequences in the Fd fragment of rabbit immunoglobulin heavy chains

The sequence has been completed of the N-terminal 94 residues of the variable section of the Fd fragment of heavy chains from rabbit immunoglobulin G (IgG) of allotype As1. Most of the sequence of the same section from IgG of allotype Aa3 is also reported. These results, in conjunction with a substantial sequence of the variable region of allotype Aa2 reported elsewhere (Fleischman, 1971), show the presence of 16 positions (including six consecutive positions) in which the residue present correlates with the allotype. No allotype-related sequence variation has been found in the constant section of the Fd fragment. This evidence supports the view that two genes code for the heavy chain and it can be used as evidence in favour of somatic mutation as the origin of the variability in the sequence of the N-terminal section. The evolutionary origin of the ;a' locus allotypes of rabbit immunoglobulins remains obscure.     

beta2-Microglobulins: isolation, properties, and distribution.

beta2-Microglobulin is structurally related to immunoglobulin domains and is identical to the light chain of histocompatibility (HL-A) antigens. Similar to free light chains of immunoglobulins, beta2-microglobulin is most easily isolated from urine. We have previously purified human beta2-microglobulin from urine of patients with renal tubular resorption defects. Corresponding proteins have now been obtained from urine of rabbits and guinea pigs treated with sodium chromate. Sequence studies have established that the rabbit protein is rabbit beta2-microglobulin. The guinea pig protein closely resembles the human and rabbit beta2-microglobulins in amino acid composition, charge, molecular size, and also in the presence of an apparently analogous disulfide loop. These findings indicate that this protein is the guinea pig homologue of beta2-microglobulin. Physical-chemical studies suggest that human beta2-microglobulin and isolated immunoglobulin domains are similar not only in amino acid sequence but also in three-dimensional structure. Both types of molecules are compact and globular in shape and apparently contain beta-pleated sheet conformation. beta2-Microglobulin is present in free form in various body fluids and as a subunit of histocompatibility antigens on cell surfaces. Current estimates suggest that the number of beta2-microglobulin molecules on cell surfaces is higher than the number of histocompatibility (HL-A) antigens. Accordingly, beta2-microglobulin is possibly a subunit of additional cellular antigens or receptors.     

Isolation and partial characterisation of immunoglobulin from southern bluefin tuna Thunnus maccoyii Castelnau

Specific and total serum immunoglobulins were extracted by immunoaffinity, mannan-binding protein and Protein A affinity chromatography from southern bluefin tuna (Thunnus maccoyii Castelnau) immunised with rabbit IgG, and from non-immunised southern bluefin tuna. SDS-PAGE in 10% reducing gels revealed two heavy chains with molecular weights of approximately 74.6 +/- 1.3 kDa and 71.2 +/- 0.9 kDa, and two light chains with molecular weights of approximately 29 +/- 1.2 kDa and 28 +/- 1.0 kDa. Under non-reducing, but denaturing, conditions in 4% and 5% SDS-PAGE gels, a high molecular weight and a low molecular weight fraction were demonstrated. By gel filtration using Sephacryl HR 300 a molecular weight of 845 kDa, consistent with a tetramer, was obtained for the high molecular weight fraction, and a molecular weight of 168 kDa, consistent with a monomer, was obtained for the low molecular weight fraction. The extinction coefficient at A280 for the purified immunoglobulin (Ig) was determined to be 1.24. Tuna a-rabbit IgG Ig was reactive with all non-reduced mammalian IgG antigens tested, suggesting that common conformational antigenic determinants were recognised.     

Oligoclonal β-galactoside-binding immunoglobulins antigenically related to 14kda lectin in human serum and cerebrospinal fluid: Purification and characterization

• 1.1. An antiserum raised against a 14kDa β-galactoside specific lectin from human brain (HBL14) was used to probe blots from samples of serum and cerebrospinal fluid. The only HBL14-immunoreactive material detected was heavy and light chains of a β-galactoside-binding IgG fraction (lectin-like IgG).
• 2.2. Lectin-like IgG, as well as IgG Fab fragments, compete with HBL14 for binding either to anti-HBL14 antibody or to a lactosyl polyacrylamide-based copolymer.
• 3.3. Purification of lectin-like IgG was obtained by affinity chromatography on immobilized rabbit anti-lectin immunoglobulins. The carbohydrate-binding specificity of the purified molecules was restricted to β-Gal-containing structures and close to the HBL14 one.