A solid phase fluorescent immunossay for the quantitation of the C4 component of human complement

Granulocyte colony-stimulating factor in acute myeloid leukemia

The clinical application of recombinant human G-CSF in patients with acute myeloid leukemia (AML) has been controversial because it stimulates the in vitro proliferation of leukemic cells. In order to explore the possibility of predicting in vivo leukemic proliferation after G-CSF administration to AML patients by using in vitro assays, we investigated the leukemic blasts of 30 AML patients, including 14 patients who received G-CSF for severe infection associated with neutropenia following chemotherapy (G-CSF group) and 16 patients who did not (control group). Of the 14 patients in the G-CSF group, 9 showed an increase of leukemic blasts in the peripheral blood during G-CSF administration, while 11 of the 16 control patients developed leukemic resurgence. In the G-CSF group, the frequency of leukemic resurgence among patients whose blasts showed dose-dependent proliferation after addition of G-CSF to cultures was similar to that among patients whose blasts did not. In addition, there were no significant differences between the G-CSF and control groups in [3H]thymidine incorporation by leukemic cells and leukemic colony formation after the addition of G-CSF to cultures. The G-CSF receptor affinity of leukemic blasts was significantly higher in the patients with leukemic resurgence (mean dissociation constant [Kd]: 55 pM in the G-CSF group and 63 pM in the control group) than in those without it (101 pM and 96 pM, respectively), and the number of G-CSF receptors per cell was significantly lower when leukemic resurgence occurred (200 in the G-CSF group and 260 in the control group) than when it did not (3400 and 3030, respectively). Immunophenotyping (for CD2, CD7, CD10, CD13, CD19, CD33, CD34, CD71, HLA-DR, glycophorin A and the G-CSF receptor) revealed no significant differences between blasts from the patients with and without leukemic resurgence in the G-CSF group. Thus, we conclude that the in vivo leukemic resurgence during G-CSF administration after chemotherapy for AML was not correlated with the in vitro responsiveness of leukemic blasts to this cytokine or with blast phenotyping data. Leukemic resurgence is likely to occur in patients whose leukemic blasts have fewer numbers of G-CSF receptors with a high affinity irrespective of whether patients receive G-CSF.

Bladder Cancer Cells Express Functional Receptors for Granulocyte-Colony Stimulating Factor

The effects of human recombinant granulocyte-colony stimulating factor (G-CSF) on the growth of cultured human bladder cancer cells and G-CSF receptor on these cells were investigated. Human bladder cancer cell lines, KU-1 or NBT-2, were incubated with and without G-CSF. At 48 hours, 3H-thymidine uptake of both cells was significantly higher with G-CSF (one ng./ml., 10 ng./ml.) than that of control without G-CSF (p less than 0.05). The binding of 125I-labeled KW-2228, a muteins of G-CSF, to KU-1 and NBT-2 was inhibited by unlabeled KW-2228 in a dose-dependent manner. These results demonstrated that G-CSF stimulates the clonal growth of human bladder cancer cells by binding to its specific receptors.

Mutant protein of recombinant human granulocyte colony-stimulating factor for receptor binding assay

A new mutant protein of recombinant human granulocyte colony-stimulating factor (rhG-CSF) was produced for the studies on receptors for human G-CSF. The mutant protein [(Tyr1, Tyr3]rhG-CSF), the biological activity of which was almost equal to that of rhG-CSF, was prepared by the replacement of threonine-1 and leucine-3 of rhG-CSF with tyrosine. The radioiodinated preparation of the mutant protein showed high specific radioactivity and retained full biological activity for at least 3 weeks. The binding capacity of the radioiodinated ligand was compared with that of [35S]rhG-CSF. Both radiolabeled ligands showed specific binding to murine bone marrow cells. Unlabeled rhG-CSF and human G-CSF purified from the culture supernatant of the human bladder carcinoma cell line 5637 equally competed for the binding of labeled rhG-CSFs in a dose-dependent manner, demonstrating that the sugar moiety of human G-CSF made no contribution to the binding of human G-CSF to target cells. In contrast, all other colony-stimulating factors and lymphokines examined did not affect the binding. Scatchard analysis of the specific binding of both labeled ligands revealed a single class of binding site with an apparent dissociation constant (Kd) of 20-30 pM and 100-200 maximal binding sites per cell. These data indicate that the radioiodinated preparation of the mutant protein binds the same specific receptor with the same affinity as [35S]rhG-CSF. The labeled mutant protein also showed specific binding to human circulating neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Granulocyte colony-stimulating factor (G-CSF) receptors on acute myeloblastic leukaemia cells and their relationship with the proliferative response to G-CSF in clonogenic assay

The number and the affinity of granulocyte colony-stimulating factor (G-CSF) receptors expressed by blast cells in acute myeloblastic leukaemia (AML) were determined using radiolabelled recombinant human G-CSF (rhG-CSF). Eighteen of 20 patients demonstrated specific binding, and Scatchard analysis revealed a single class of high affinity (Kd 15-130 pM) G-CSF receptors on the AML blasts. The number of G-CSF receptors varied from 55 to 1,200 per cell (mean 278). In the remaining two patients, specific binding was not observed. The number of G-CSF receptors did not differ significantly between various AML subtypes, but the mean receptor number was the highest on type M2 blasts. A chemical cross-linking study revealed that the G-CSF receptor has an approximate molecular weight of 140,000. Autoradiography showed heterogeneity of the distribution of G-CSF receptors on the AML blasts obtained from a single patient. The number of colonies stimulated by the addition of rhG-CSF varied from 0 to 566 per dish, and blast colony formation was observed in eight of 20 patients. The population mean of G-CSF receptor number expressed by blasts that formed colonies on stimulation with rhG-CSF was significantly higher than that on blasts which did not form colonies. These results suggest that a proliferative response of AML blasts to G-CSF may be predicted when the blasts express a large number of G-CSF receptors. Accordingly, it may be safer to restrict the clinical use of G-CSF to AML patients who have blasts with a low G-CSF receptor expression and no response to G-CSF in blast colony assay.

Identification and characterization of receptors for granulocyte colony-stimulating factor on human placenta and trophoblastic cells

Since radioiodination of human granulocyte colony-stimulating factor (G-CSF) is difficult, we synthesized a mutein of human G-CSF that retains full biological activity and receptor-binding capacity for at least 2 weeks after radioiodination. Receptors for human G-CSF were characterized in the plasma membrane fraction from the human term placenta (human placental membranes) and trophoblastic cells by using the 125I-labeled mutein of human G-CSF (KW-2228). The specific binding of 125I-labeled KW-2228 to placental membranes was pH-dependent, with maximal specific binding at pH 7.8; it increased linearly with protein to 3.7 mg of protein per ml and was both time- and temperature-dependent, with maximal binding at 4 degrees C after a 24-hr incubation. When we examined the ability of hematopoietic growth factors to inhibit 125I-labeled KW-2228 binding, we found that KW-2228 and intact human G-CSF inhibited 125I-labeled KW-2228 binding, whereas erythropoietin or granulocyte-macrophage colony-stimulating factor did not. Scatchard analysis revealed a single receptor type with a Bmax of 210 fmol/mg of protein and a Kd of 480 pM. The human G-CSF receptors on human placental membranes were shown to consist of two molecular species of 150 kDa and 120 kDa that could be specifically cross-linked to 125I-labeled KW-2228. Human trophoblastic cells, T3M-3, also possessed a single receptor for G-CSF with a Bmax of 533 receptors per cell and a Kd of 390 pM. Thus we have identified the receptor for human G-CSF on human placental membranes and trophoblastic cells, and the presence of this receptor in these membranes suggests that human G-CSF plays some role in the feto-placental unit during human development.

Comparison of colorimetric, fluorescent, and enzymatic amplification substrate systems in an enzyme immunoassay for detection of DNA-RNA hybrids

The monoclonal antibody solution hybridization assay is a novel enzyme immunoassay for detection of RNA with a biotinylated DNA probe. To increase the sensitivity of this test, a fluorescent substrate and an enzymatic amplification cycling system were compared with a conventional colorigenic substrate for alkaline phosphatase. The fluorescent, cycling, and colorigenic substrates detected, respectively, 10, 10, and 100 amol of unbound alkaline phosphatase in 2 h. With a prolonged incubation period of 16.6 h, the conventional substrate measured 10 amol of the enzyme. In the immunoassay for RNA detection, the fluorescence and cycling assays were faster than that using the colorigenic substrate and reached an endpoint sensitivity of 3.2 pg/ml (0.16 pg per assay) of cRNA. However, longer incubation periods (16.6 h) for optimal generation of the colorigenic product led to a comparable level of sensitivity for the conventional substrate.

Loss of transferrin receptor activity in Neisseria meningitidis correlates with inability to use transferrin as an iron source

Although Neisseria meningitidis does not produce siderophores, it is able to obtain iron from human transferrin. We observed saturable specific binding of 125I-labeled human transferrin to meningococci. Human lactoferrin and mouse transferrin did not compete with human transferrin for binding, whereas human apotransferrin and 100% iron-saturated transferrin competed equally well. Meningococci thus have a specific receptor for human transferrin. Scatchard analysis yielded a relatively low Kd of 0.7 microM and an apparent copy number of 2,900 receptors per CFU. Receptor activity was iron-regulated. A meningococcal transformant specifically unable to utilize transferrin as an iron source had decreased transferrin receptor activity. These data are consistent with the hypothesis that receptor-mediated binding of transferrin is a rate-limiting step in meningococcal iron uptake from transferrin.

Characterization of receptor for granulocyte colony-stimulating factor on human circulating neutrophils

We have made a mutein of human G-CSF with more stable, and potent biological activity. Using 125 I-labeled mutein human G-CSF, high affinity binding sites were identified on human circulating neutrophils. Receptor number per cell was 560 with a Kd of 250 pM. The human G-CSF receptor was identified as a single subunit protein of Mr approximately 150,000.

Oxidative radioiodination damage to human lactoferrin

Oxidative iodination of human lactoferrin (Lf) as commonly performed by using the chloramine-T, the Iodogen or the lactoperoxidase method produces an unreliable tracer protein because of excessive and heterogeneous polymer formation. Before iodination a minor tetramer fraction may be demonstrable in iron-saturated Lf only. Iodination-induced polymerization of iron-poor as well as iron-saturated Lf occurs independently of the presence or absence of 10 mM-EDTA and the 125I-/Lf molar ratio used for iodination. 125I-Lf polymers are mainly covalently linked, as suggested by the lack of substantial dissociation in SDS/polyacrylamide-gel electrophoresis. Damage to the 125I-Lf monomer may be another consequence of oxidative iodination. This is demonstrated in SDS/polyacrylamide-gel electrophoresis where 50% of the radioactivity of apparently normal monomer (Mr 75,000) is displaced to a lower-Mr region (30,000-67,000) after reduction with dithiothreitol. Non-oxidative iodination by the Bolton-Hunter technique produces an antigenetically stable tracer that is not being subjected to polymerization and monomer degradation as judged by high-performance gel chromatography and SDS/polyacrylamide-gel electrophoresis with and without dithiothreitol treatment. It is concluded that oxidation in itself leads to covalent non-disulphide cross-linking between human Lf molecules and, possibly, to intramolecular peptide-bond breaking becoming unmasked under reducing conditions. In biological experiments with human 125I-Lf this problem should be carefully considered.

A solid phase fluorescent immunoassay for the rapid detection of virus antigen or antibodies in fetuses infected with porcine parvovirus

A solid phase fluorescent immunoassay using polyacrylamide beads coated with rabbit anti-porcine parvovirus antibodies has been developed and utilized in the diagnosis of porcine parvovirus infection. The antibody-coated beads (immunobeads) were used both to detect virus in mummified fetal tissues and to demonstrate specific antibodies in serum and ovarian follicular fluid. The immunobeads assay (IBA) was as sensitive as ELISA but more sensitive than virus isolation using tissue culture and haemagglutination tests. Both mummified and normal fetuses were obtained after experimental infection of SPF pregnant gilts. Using immunobeads, porcine parvovirus antigen was found in all mummified fetuses, but was found in only 1 out of 17 normal fetuses.

Mechanism and characteristics of platelet activation by haematin

The mechanism as well as some characteristics of haematin-induced human platelet aggregation were investigated. Haematin-induced platelet aggregation required the presence of devalent cations; Mg2+, and to a lesser extent, Co2+, were just as effective as Ca2+ in supporting the aggregation. Mono- and trivalent cations were ineffective. Verapamil inhibited the aggregation. The aggregation was accompanied by thromboxane formation which could be abolished by aspirin. The release of adenine nucleotides was only slightly inhibited by aspirin. The rate of aggregation and the ultrastructure of the aggregated platelets were comparable between control and aspirin-treated samples. It is concluded therefore that haematin-induced aggregation is not dependent on platelet prosta-glandin synthesis. Haematin induced binding of fibrinogen to platelets, and failed to aggregate thrombasthenic platelets. These findings indicate that haematin may induce platelet aggregation by promoting influx of divalent cations in association with increased fibrinogen binding and release of adenine nucleotides.

Detection and characterization of mouse monoclonal antibodies to epidemic typhus rickettsiae

A solid-phase immunofluorometric assay was used to detect mouse monoclonal antibodies to epidemic typhus rickettsiae, Rickettsia prowazekii (the immunizing antigen), and to murine typhus rickettsiae, Rickettsia typhi, a related antigen. Of the 649 hybridoma cultures obtained, 628 contained antibodies either to R. prowazekii or to both R. prowazekii and R. typhi. A total of 72 cultures were cloned by limiting dilution and yielded 137 antibody-producing clones. Of these, 104 produced antibodies specific for R. prowazekii, 22 produced antibodies that reacted with R. prowazekii and R. typhi, and 11 produced antibodies that reacted with R. prowazekii, R. typhi, and R. canada. The immunoglobulin isotypes of the mouse monoclonal antibodies produced were identified by a related indirect immunofluorometric assay technique with fluorescein isothiocyanate-conjugated antisera specific for each isotype. Antibodies were also evaluated by indirect fluorescent antibody tests, and antibodies from selected clones were found to neutralize rickettsial toxic activity in mice.

A solid-phase fluoroimmunoassay for human IgE

A fluoroimmunoassay (FIA) for the measurement of immunoglobulin E (IgE) is described. The method involves a sandwich technique in which antiserum to human IgE is adsorbed on a cellulose acetate/nitrate disc which is attached to a plastic StiQTM sampler. The prepared sampler is reacted with serum and antigen is bound specifically. After buffer wash and treatment with goat serum to block non-specific binding, the samplers are reacted with monospecific fluorescein conjugated antisera to human IgE. Two buffer washes remove unbound material and the fluorescence which is directly proportional to the IgE concentration is measured in a FIAX fluorometer. Assay standards range from 2 to 400 IU/ml. The method gives within run coefficients of variation (CV) from 3.3 to 8.4% and between run CV from 6.2 to 16.1% being less precise at low analyte concentrations. IgE concentrations of a group of 74 sera determined by FIA using StiQsTM prepared with antisera from 2 sources correlated well with results found by radioimmunoassay.

Characterization of antibody responses in legionellosis with an immunofluorometric assay

A solid-phase immunofluorometric assay was used to qualitatively characterize and precisely measure human immunoglobulin class-specific antibody responses in legionellosis. Stable antigen preparations consisted of cells grown at 25 degrees C that were killed, fixed with Formalin vapors, washed, and lyophilized. Working-curve material consisted of dilutions of selected convalescent sera. Linear regressions of logit transformations of relative fluorescence intensities versus the logarithm of the relative concentrations of sera were determined to give immunoglobulin class-specific antibody levels from uninfected and infected individuals. Each fluorescence intensity obtained with immunoglobulin class-specific antibody was converted to a multiple of the median fluorescence intensity obtained with sera from uninfected individuals. A presumptive-positive acute-phase legionellosis serum was defined for each immunoglobulin class by a multiple of the normal median fluorescence intensity that was greater than the multiple of the normal median from approximately 97% of the uninfected population.

Quantitation of rat liver xanthine oxidase by radioimmunoassay. A mechanism for sex-specific differences

To further delineate the mechanism responsible for the differences in xanthine oxidase activity in male and female Sprague-Dawley rats, a sensitive and specific radioimmunoassay (RIA) was developed for the measurement of hepatic xanthine oxidase. The RIA could detect as little as 5 mg of liver enzyme. Specificity of the RIA was confirmed by 1) Ouchterlony double immuno-diffusion in which a single precipitin band exhibited xanthine oxidase activity, when crude liver homogenate and an enzyme-specific stain were used; 2) parallelism between purified 125I-labeled xanthine oxidase and serial dilutions of crude liver homogenate; 3) a linear correlation between xanthine oxidase activity and the level of enzyme protein; and 4) a single protein band coincident with purified xanthine oxidase, when an immunoprecipitate prepared from antisera and crude liver homogenate was analyzed on sodium dodecyl sulfate (SDS) polyacrylamide gels. Whether xanthine oxidase activity was assayed in the absence of nicotinamide adenine dinucleotide (NAD+) (oxidase form) or in the presence of NAD+ (dehydrogenase), male values were consistently higher, and both forms of the enzyme correlated significantly with each other. When purified to homogeneity, neither form of the enzyme was appreciably affected by 17 beta-estradiol or testosterone propionate. When the RIA was employed, levels of hepatic xanthine oxidase were significantly greater in male than in female rats. We concluded from these data that increased xanthine oxidase activity in the male corresponds to a greater quantitative complement of xanthine oxidase protein. Furthermore, lower xanthine oxidase activity in the female cannot be explained by immunologically cross-reactive material without enzyme activity nor by a direct sex-steroid enzyme interaction.

A novel non-separation fluoroimmunoassay for thyroxine

It has proved possible to develop a novel non-separation fluoroimmunoassay for thyroxine employing antibodies both to thyroxine and to fluorescein incorporated into immune complexes by addition of a common species-specific anti-immunoglobulin G serum. The labelled hapten could bind to antibody of either specificity but not to both at the same time. Binding to anti-fluorescein markedly reduced fluorescence whereas binding to anti-thyroxine did not. Unlabelled thyroxine competed with the labelled hapten only for anti-thyroxine binding sites and, as a result, more of the labelled thyroxine was bound to anti-fluorescein with a decrease in total fluorescence.

Quantitation of serum immunoglobulins

This article reviews critically the current "state of the art" in the quantitation of immunoglobulins in serum and other body fluids. The methodologies reviewed include (a) those occurring in solution, for example, automated immunoprecipitin and laser nephelometric techniques, rate analysis techniques and radioimmunoassays; (b) techniques involving radial diffusion in agarose gels, with and without secondary development steps; and (c) those techniques involving solid supports, such as fluoroimmunometric assays and solid phase radioimmunoassays. The theory of each technique is presented with an analysis of the strengths and weaknesses, particularly sources of error, and the techniques are compared in terms of accuracy, precision, sensitivity, test cost, equipment cost, feasibility for use in different laboratory settings, and ease of handling. Problems associated with the antisera used, with standards, and with quality controls are discussed and solutions suggested.

Detection of monoclonal influenza antibodies synthesized in culture by hybridoma cells with a solid-phase indirect immunofluorometric assay

A solid-phase indirect immunofluorometric assay for measuring reactions of mouse monoclonal antibodies with antigen has been developed, with influenza virus as a model. Purified IgG from hyperimmune rabbit sera is covalently linked to polyaminostyrene beads, to which influenza viruses are then bound immunologically to make solid-phase antigens. Alternatively, the virus is covalently coupled directly to the beads. Mouse antibodies, produced by hybridoma cells in culture, are reacted with constant amounts of solid-phase antigens, and then indirectly quantitated by adding FITC-labeled antimouse Ig and measuring the fluorescent intensity with a filter-fluorometer. The assay system permits rapid screening for low levels of antibodies synthesized by hybridoma cells in culture. It is about 25- to 150-fold more sensitive than hemagglutination inhibition tests in detecting monoclonal antibodies reactive with influenza virion HA protein.

Fluorescence immunoassay based on long time correlations of number fluctuations

We report the development of a fluorescence-based immunoassay technique relying on the physical phenomena of random number fluctuations and diffusion, which we review. By determining the autocorrelation of the fluctuations in the fluorescent intensity, this methid is able to measure the amount of labeled antigen or antibody that is bound to micrometer-sized carrier particles in solution. The principal advantage of this technique is its insensitivity to small, fast-diffusing sources. It also discriminates against weakly fluorescent contaminants of size comparable to the carrier particles. We demonstrate these attributes by using two model systems: a human IgG assay and an idealized system consisting of polystyrene fluorescent spheres and rhodamine dye.

A solid phase immunofluorescent assay for the measurement of salivary immunoglobulin and albumin levels

A solid phase immunofluorescence assay which can be used to measure immunoglobulin and albumin levels in whole saliva, as well as in duct collected saliva samples, is described. This method is about an order of magnitude more sensitive than the conventional radial immunodiffusion method, allowing its use in situations involving large numbers of samples or restricted sample volumes. The relative precision and accuracy of this method are comparable to those of radial immunodiffusion.

Quantitative characterization of specificity and potency of conjugated antibody with solid-phase, antigen bead standards

An immunofluorescent assay was used to characterize precisely the potency and specificity of fluorescein-conjugated immunoglobulin class-specific and polyvalent anti-sera. Stable antigen standards consisted of highly purified immunoglobulin antigens covalently bound to polyaminostyrene beads. Linear regressions of weighted logit transformations of relative fluorescent intensities versus the logarithm of relative conjugate concentrations were determined. The potency of conjugates was compared using two different methods derived from the logit transformation. Inappropriate specificities were measured in some conjugates described as immunoglobulin 'class-specific'.

A quantitative assay for low levels of IgM by solid-phase immunofluorescence

A quantitative immunofluorescent assay capable of detecting between 15 and 1450 ng of IgM on a strictly linear standard curve has been developed. The assay system is unique in that in vitro biosynthesized polyclonal IgM in culture supernatants can be quantitated with a minimal quantity of supernatant. Interference created by lectins and bead-surface interactions have been analyzed. This easily operated assay has been validated and is reliable. A very important feature of the system is the considerable cost reduction in comparsion with radiometric techniques.