Use of protein A-coated colloidal gold particles for immunoelectronmicroscopic localization of ACTH on ultrathin sections

ACTH was localized in dissociated porcine adenohypophysial cells using a novel indirect EM immunocytochemical technique. Incubation of ultrathin resin sections in anti-ACTH was followed by incubation with protein A-coated colloidal gold particles. Protein A binds specifically to the Fc part of the IgG molecule, and thus the ACTH-containing secretory granules became labelled with electron-dense gold particles. With this method, the dissociated porcine ACTH cells was identified as containing numerous round or ovoid 170--300 nm secretory granules.

Effects of serum and cations on the selective release of granular proteins from human netrophils during phagocytosis

The extracellular release from human neutrophils of the primary (azurophil) granule constituents, myeloperoxidase (MPO), chymotrypsin-like cationic protein (CCP), collagenase and lysozyme, and the secondary (specific) granule constituents, lactoferrin and lysozyme, was measured during ingestion of staphylococcus protein-A-IgG complexes. In buffer, lactoferrin release was consistently higher than that of the other protein. In serum, lactoferrin release increased concomitantly with ingestion, whereas the rate of lysozyme and especially of MPO release were stimulated to a higher degree than ingestion. Magnesium (0.5--2 mM) was more potent than calcium (0.5--2 mM) in promoting release but these cations worked synergistically. Zinc (0.5--4 mM) was found to be a potent and selective inhibitor of collagenase release. Manganese (0.25--4 mM), which inhibited the ingestion of SpA-IgG complexes, also inhibited release of CCP, collagenase, lysozyme and MPO, but actually stimulated lactoferrin release. The data suggests that lactoferrin and lysozyme may be confined to distinct granule populations or else released in a different fashion from the granules. When the effects on release of primary granule proteins are concerned it is suggested that the dissociation of binding of various agents to an anionic granule matrix may be affected differently by various cations.

Sensitive and convenient quantitation of antibody binding to cellular antigens using glutaraldehyde preserved cells

As a preliminary step in the identification and isolation of antibodies to human cancers, we have developed a sensitive and convenient assay for antibody binding to cellular antigens. The basis for the method is antibody binding to glutaraldehyde-fixed cells (AbGfC) and quantitation with radioiodinated staphylococcal protein A (SpA). Glutaraldehyde fixation of intact cells, which does not appear to effect the ability to form antigen-antibody complexes, provides a convenient and standard supply of target cells which may be stored at 4 degrees C and used in the assay over a period of several months. The amount of antibody specifically bound to the cells is quantitated by the addition of 125I-labeled SpA. The sensitivity of the method was compared with two complement-dependent cytotoxicity methods (trypan blue exclusion and 51Cr release assays) and tested with two antisera to human lung cancer and one antiserum to a membrane antigen of a murine lymphoma. These comparisons indicated much greater sensitivity when compared with the trypan blue exclusion assay and equivalent sensitivity with greater dose response characteristics when compared with the 51Cr release assay.

Use of protein A--containing Staphylococcus aureus as an immunoadsorbent in radioimmunoassays to separate antibody-bound from free antigen

Heat killed, formalinized Cowan I strain Staphylococcus aureus (PASA) was examined for its utility as a solid-phase immunoadsorbent in various RIA procedures. Specific antibody could be adsorbed to PASA and then reacted with radiolabeled and unlabeled hormone, or alternatively, PASA could be added to antibody-hormone mixture in order to separate antibody-bound from free antigen. Both methods compared favorably with the more standard double-antibody method in each system tested. Antibodies produced by rabbits, guinea pigs, monkeys, and humans were precipitated equally by PASA and double antibody, whereas antibody raised in sheep was precipitated much less by PASA than by double antibody. Antibody bound to PASA was found to reach equilibrium of binding more slowly than unbound antibody for both rapid (TRH) and slow (rPRL) reactions. Binding of either free of complexed IgG by PASA, however, was extremely rapid, reaching equilibrium in less than 30 sec. This rapid binding was utilized in kinetic experiments which would not have been possible with slower-reacting precipitating agents. The versatility permitted by this propertly constitutes one of the most useful characteristics of PASA. Other important attributes of PASA include its convenience, economy, and wide applicability.

Protein A-positive staphylococci serve as a selective B cell mitogen for lymphocytes from primary immunodeficiency patients

Staphylococcus aureus protein A-positive bacteria have recently been proposed as selective B lymphocyte mitogens. We have studied the lymphocyte response to such mitogens in bacteria in normal subjects and in patients with primary immunodeficiencies. Patients with primary T cell defects show a normal response to protein A-positive bacteria and impaired responses to PHA and Con A. In contrast, patients with Bruton agammaglobulinaemia respond normally to these T cell mitogens but not to the bacteria. Thus, protein A-positive bacteria fulfil the criteria for being a T cell-independent B cell mitogen for human peripheral blood cells.

Immunoassay of indomethacin: the use of [125I] protein A to detect specific serologic binding

The sera of rabbits that were injected with indomethacin covalently linked to human albumin bound increasing amounts of [14C] indomethacin during the course of immunization. The serum-binding components chromatographed with the gamma-globulin fraction and were precipitated with goat-anti-rabbit-gamma-globulin. When measured by radioimmunoassay with [14C] indomethacin under optimal conditions, 34 ng (95 pmoles) of unlabeled indomethacin inhibited [14C] indomethacin binding 50%. The antibodies reacted most effectively with indomethacin and the desmethylated analogue, 1-(p-chlorobenzoyl)-2-methyl-5-hydroxyindole-3-acetic acid, but not 2-methyl-5-methoxy-indole-3-acetic acid. An immunoassay based on the use of [125I] Protein A as tracer for IgG antibody was developed for quantitative determination of indomethacin at the picogram level. Indomethacin, immobilized by covalent linkaae to a solid support, bound the rabbit anti-indomethacin. Protein A, labeled with [125I], measured the levels of the bound IgG antibody. Fluid phase indomethacin competed with solid-phase indomethacin for the anti-indomethacin, which resulted in decreased anti-indomethacin and consequently decreased [125I] Protein A on the immobilized indomethacin-anti-indomethacin complex. The serologic specificity with the immobilized ligand immunoassay was the same as that found with the [14C] indomethacin radioimmunoassay, but the sensitivity for detection of indomethacin was increased over 300-fold.

A radioimmunometric antibody-binding assay for evaluation of xenoantisera to melanoma-associated antigens

A radioimmunometric antibody-binding assay was developed with the use of 125I-labeled protein A of Staphylococcus aureus (SpA) for the evaluation of xenoantisera to human melanoma-associated antigens. Antisera were produced in New Zealand male albino rabbits by the injection of cultured human melanoma cells or soluble, partially purified melanoma-associated antigens isolated from these cells. Xenoantisera were rendered operationally specific for melanoma-associated antigens by absorption with human red cells and cultured lymphoblasts. The methodologic parameters and the quantitative relationships among xenoantisera, cultured melanoma target cells, and 125I-labeled SpA and their effect on the measurement of xenoantibody binding were critically evaluated. Data indicated the usefulness of the radioimmunometric assay in monitoring the efficacy of absorption and in characterizing the specificity of xenoantisera to melanoma-associated antigens. The radioimmunometric binding assay when modified and used as a binding inhibition assay was effective in the assessment of the serologic activity of soluble melanoma-associated antigens and thus may be used to monitor the progress of antigen purification.

Separation of cell-dependent antibody (CDA) and inhibitory antibody by protein-A affinity chromatography and the effect of fractions on antibody-dependent cellular cytotoxicity (ADCC)

The nature of cell-dependent antibody (CDA) and the mechanism of inhibition of antibody-dependent cellular cytotoxicity (ADCC) were studied in the ADCC assay system in which culture cells of methylcholanthrene-induced rat fibrosarcoma (KMT-50) were used as target cells, xenogeneic antiserum (rabbit anti-KMT-50) as the CDA, and human peripheral blood leucocytes (PBL) as effector cells, respectively. By using protein-A Sepharose CL-4B affinity column chromatography of rabbit anti-KMT-50 serum, CDA was shown to bind protein A. Complement dependent-cytotoxicity (CDC), however, was demonstrated in both the adsorbed fraction (eluate) and the non-adsorbed fraction (effluent) to protein A from the same affinity column chromatography. These data confirmed that CDA was IgG with an intact Fc portion. Inhibition of ADCC occurred by pretreatment of effector cells with rabbit anti-effector (human PBL) serum even with extremely small amounts of antiserum. Such inhibition was demonstrated with the eluate but not with the effluent from protein-A Sepharose CL-4B affinity column chromatography of rabbit anti-effector serum. F(ab')2 fragments of the same eluate (IgG) did not inhibit the ADCC activity. These data showed that the inhibition of ADCC was induced by the blocking of Fc receptors of effector cells with the Fc portions of IgG in anti-effector serum. The data obtained indicate the usefulness of protein A in separation and analysis of CDA and in investigation of the inhibitory mechanisms of ADCC.

The use of immobilized ligands and [125I]protein a for immunoassays of thromboxane B2, prostaglandin D2, 13,14-dihydro-prostaglandin E2, 5,6-dihydro-prostaglandin I2, 6-keto-prostaglandin F1 alpha, 15-hydroxy-9 alpha, 11 alpha(epoxymethano)prosta-5,13-dienoic acid and 15-hydroxy-11 alpha,9 alpha(epoxymethano)prosta-5,13-dienoic acid

Immunoassays were developed for quantitative determination of thromboxane B2, prostaglandin D2, 13,14-dihydro-prostaglandin E2, 5,6-dihydro-prostaglandin I2, 6-keto-prostaglandin F1 alpha, 15-hydroxy-9 alpha, 11 alpha (epoxymethano) prosta-5, 13-dienoic acid and 15-hydroxy-11 alpha, 9 alpha (epoxymethano) prosta-5,13-dienoic acid. Ligands immobilized by covalent linkage to a solid support, bound homologous rabbit antibodies. [125I] Protein A was used to measure the bound IgG antibody. Increments of homologous and heterologous fluid-phase ligand completed with solid-phase ligand for antibody and resulted in decreasing amounts of bound [125I]-Protein A. The serologic specificity for each immune system was determined. Immunoassays for thromboxane B2, 6-keto-prostaglandin F1 alpha, and 5,6-dihydro-prostaglandin I2 were used to identify their respective homologous ligands that were separated by normal phase and reversed phase high pressure liquid chromatography.

A rapid method for the purification of antibody--enzyme conjugates

A method is described for a rapid and efficient separation of enzyme-labelled antibodies from the free enzyme following the coupling reaction. A single passage of the reaction mixture on a protein A--Sepharose CL-4B column gave a sharp separation of the free enzyme from the conjugate.

Serum proteins and secretory component in human carious dentin

By the use of the peroxidase-labeled antibody method, significant localization of IgG, IgA, albumin and transferrin was demonstrated in the deep lesion of 20 carious teeth, where the secretory component was absent. These serum proteins formed a distinct zone, surrounding the overlying, shallow lesion infected with bacteria.

Studies on the identification of B lymphocytes using protein A. Lymphocytes of human palatine tonsil

The prinicpal methods presently being applied to distinction of the subpopulations of lymphocytes consist in the E-rosette method for T cells and the EAC-rosette method for B cells. However, it has been learned that other cells have the ability to form rosettes. B cells are employed in various experiments due to the explicitly verifiable immunoglobulin on the surface of lymphocytes. However, as the fluorescent antibody method adopted as the method for verification has a number of difficulties, we tried to determine B cells by utilizing protein A, by combining protein A with SRBC (sheep red blood cells) and forming rosettes, both in human peripheral blood and in human intratonsillar lymphocytes. As a result, it was noted that lymphocytes indicating positivity existed at a level of 15-20% in human blood and 40-45% in the tonsil.

Ultrastructural localization of intracellular antigens by the use of protein A-gold complex

An immunocytochemical technique for the demonstration of intracellular antigens (secretory proteins) on thin sections is reported. Staphylococcal protein A which reacts with the Fc fragment of IgG molecules was labeled with colloidal gold as a marker. The antigenic sites were visualized on aldehyde-fixed and Epon-embedded tissue in a two step procedure. The specific antisera were applied to thin sections for binding to the antigens and then visualized by the protein A-gold complex. By using this technique different secretory proteins of the exocrine and endocrine pancreas were localized. The protein A-gold technique is proposed as a general method for visualization of antigenic sites on thin sections.

A micro immunoassay method for measuring IgG antibodies using staphylococcal protein-A

A micro radioimmunoassay procedure has been developed for assaying IgG antibodies to ragweed and grass allergen components. The method offers a rapid and reproducible procedure for estimating antibodies in human sera and is well adapted for monitoring immunological responses following hyposensitisation therapy.

Isolation of precursors of cytochrome oxidase from Neurospora crassa: application of subunit-specific antibodies and protein A from Staphylococcus aureus

A novel immunological procedure has been applied for the isolation of precursors of cytochrome oxidase. It involves antibodies to individual subunits of the oxidase and protein A from Staphylococcus aureus linked to a Sepharose support. Unassembled (free) 'subunits' as well as a labile complex containing five polypeptide components of the oxidase were isolated from mitochondrial extracts by this technique. The procedure is superior to the previously used double-immuno-precipitation method, because of its quantitative nature, its sensitivity, rapidity and versatility. Thus, sequential titrations of precursor proteins by addition of various subunit-specific immuno-globulins to an individual extract become feasible. Furthermore, the technique is suitable for the isolation of precursors on a large scale. To avoid contamination of the polypeptide preparations with immunoglobulin, the antibodies were covalently coupled to protein A, which had been previously linked to Sepharose. A radioactive preparation of unassembled subunit 1 of cytochrome oxidase was isolated by such a modified support and its cyanogen-bromide-cleavage products were compared to those of subunit 1 obtained from the assembled enzyme.

Detection of staphylococcal enterotoxins A, B, C, D, and E in foods by radioimnunoassay, using staphyloccal cells containing protein A as immunoadsorbent

A sensitive radioimmunoassay utilizing Staphylococcus aureus cells containing protein A as a coprecipitant was developed for the detection and quantitation of staphylococcal enterotoxins A, B, C, D, and E in a variety of foods. The enterotoxins were extracted from the foods by a simple and rapid procedure. The sensitivity of the assay is 1.0 ng or less of enterotoxin per g of food.

Assay of antibodies to caliciviruses by radioimmune precipitation using staphylococcal protein A as IgG adsorbent

A radioimmune assay method designated St-RIP using a staphylococcal IgG adsorbent, which potentially has broad applications to viral (and nonviral) antigen-antibody systems, was applied to detection of calicivirus antibodies. Purified 125I-labeled virions of San Miguel sea lion virus serotypes 4 (SMSV-4) and 5 (SMSV 5) were incubated with sera; the immune complexes were reacted with an immunoadsorbent, formaldehyde-fixed staphylococci (Staphylococcus aureus protein A producer, strain Cowan I), and collected by centrifugation. Broad cross-reactivity was observed among serotypes of SMSV and vesicular exanthema of swine virus (VESV), but there was no reaction with antisera to six noncaliciviruses. Antibody production in a rabbit inoculated with SMSV-5 polypeptide was monitored by St-RIP assay; reactivity with intact SMSV-4 virion antigen was slightly less than, but closely paralleled, reactivity with SMSV-5 virion antigen. Applicability of the St-RIP test to serologic survey was demonstrated with pinniped, swine, and human (laboratory personnel) sera; numerous positive St-RIP reactions suggested the occurrence of widespread contacts with caliciviruses.

Antiserums for immunofluorescent enumeration of human T lymphocytes utilizing fluoresceinated staphylococcal protein A

Five lots (100 ml or more) of heterologous antiserums specific for human T lymphocytes were prepared using human or Rhesus monkey thymocytes as immunogens. After appropriate adsorptions, these antiserums reacted by immunofluorescence with 68% of human peripheral blood mononuclear cells and 98% of human thymocytes, with E-rosette--positive cells but not with EAC-rosette--positive cells or five human B-lymphoblastoid-cell lines. Blocking experiments showed that Rhesus monkey thymocytes share thymic antigenic determinant(s) with humans. E-rosette receptors modulated independently from T-cell heteroantigens. Non-E--rosetting neoplastic T cells were identified in several patients with lymphoproliferative malignancies. Applying both the E-rosette assay and the anti-T-cell serum provides a better method of defining the biologic properties of normal and neoplastic T lymphocytes. Standardization of immunofluorescent conjugates for human T- or B-cell enumeration is simplified if large lots of well-characterized antiserums are available.