Characterization of a monoclonal antibody directed against the murine B lymphocyte receptor for IgE

A rat hybridoma producing a high-affinity IgG2a monoclonal antibody (B3B4) directed against against the murine lymphocyte IgE receptor (Fc epsilon R) was established by using purified Fc epsilon R from Fc epsilon R+ murine hybridoma B cells as immunogen. The monoclonal and polyclonal anti-Fc epsilon R inhibited the binding of IgE to the murine lymphocyte Fc epsilon R and were also used to isolate the Fc epsilon R. B3B4 specifically recognized only the 49-Kd Fc epsilon R on murine B lymphocyte as determined by immunoprecipitation and SDS-PAGE analysis. In addition to its reaction with intact Fc epsilon R, B3B4 also recognized Fc epsilon R fragments that were present in the culture media of Fc epsilon R+ hybridoma cells. The predominant fragments isolated were 38 Kd and 28 Kd by SDS-PAGE analysis. When tested for reactivity with other cell types, B3B4 was highly specific for murine B lineage cells in that it did not significantly react with Fc epsilon R on macrophages and T cells and, in addition, did not react with the high affinity mast cell Fc epsilon R. B3B4 completely blocked IgE rosetting, and a reciprocal inhibition of binding was seen in a dose-dependent fashion between IgE and B3B4, indicating a close proximity of the IgE and B3B4 binding sites. Saturation binding analysis indicated that the Fab' fragment of B3B4 bound to twice as many sites/cell as IgE, suggesting that there are two identical B3B4 determinants per 49-Kd Fc epsilon R or that the IgE binding site is formed by the association of at least two 49-Kd Fc epsilon R. However, unlike IgE, neither B3B4 nor F(ab')2-B3B4 nor Fab'-B3B4 were very effective in causing Fc epsilon R upregulation on murine hybridoma B cells; in fact, B3B4 prevented this upregulation when added in combination with IgE. These results suggest that a site-specific interaction provided only by IgE may be essential for ligand-specific upregulation. Both polyclonal and monoclonal antibodies will be useful in further studies concerning the functional relationship between the membrane Fc epsilon R and the soluble Fc epsilon R fragments.     

A polyclonal antiserum against the rabbit progesterone receptor recognizes the human receptor: biochemical characterization

Polyclonal antiserum was generated in guinea pigs immunized with the 116,000 Mr rabbit uterine progesterone receptor (PR). The PR antigen was partially purified by DEAE-cellulose chromatography and preparative sodium dodecyl sulphate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and the 116,000 Mr band excised and injected into guinea pigs. The antiserum recognized on protein blots rabbit uterine PR of Mr 116,000 and 81,000. The antiserum was judged to be specific for PR from normal and malignant human tissues as determined by sedimentation shift on sucrose gradients, immunoprecipitation studies, protein blotting, and fluorographic analysis using photolabelled samples. Comparison of protein blots probed with this polyclonal antiserum or with a recently obtained monoclonal antibody to human PR indicated that similar PR structures were recognized in rabbit and human samples by both antisera. Characterization of the polyclonal antiserum has demonstrated its suitability for investigating the immunolocalization or PR in normal and malignant human tissues as well as the receptor structure detected on protein blots.     

A polyclonal antiserum against the rabbit progesterone receptor recognizes the human receptor: immunohistochemical localization in rabbit and human uterus

A polyclonal antiserum, raised in guinea pigs immunized with the 116,000 Mr rabbit uterine progesterone receptor (PR), was used to demonstrate immunoreactive PR in frozen fixed sections of rabbit and human uterus. In both species, PR localization was exclusively nuclear. For the rabbit uterus, staining intensity was greatest in the myometrium, followed by endometrial stroma, glands, and luminal epithelium. In premenopausal human endometrium and myometrium there was intense staining of nuclei from proliferative phase glands and myometrium. In the secretory phase the glands failed to stain, yet immunostaining persisted in the myometrium.     

Evidence for a single steroid-binding protein in the rabbit progesterone receptor

The rabbit uterine progesterone receptor copurifies as two molecular weight (Mr) forms of about 105,000 and 78,000. To investigate whether these are different proteins, we have used protease digestion, reversible denaturation, and photoaffinity labeling in studies on the steroid-binding domain of the receptor. Digestion of the Mr 105,000 and 78,000 forms, photoaffinity labeled with [3H]R5020, with Staphylococcus aureus V8 protease revealed identical peptide fragments of Mr 43,000, 39,000, and 27,000-30,000. When receptor in cytosol was denatured, separated by electrophoresis, and then reconstituted, [3H]progesterone bound specifically to a single form at about Mr 105,000. After partial purification, the reversible denaturation procedure revealed both the larger and the smaller progesterone-binding species similar to the photoaffinity-labeled species in this preparation. Receptor in uterine cytosol prepared under mild conditions appeared as a predominant large molecular weight form on photoaffinity labeling with [17 alpha-methyl-3H]R5020, [6,7-3H]R5020, or [3H]RU27987. Further purification of this cytosol showed the generation of a smaller labeled species. These results from three different approaches reinforce the view that the rabbit progesterone receptor contains a single steroid-binding protein.     

Characterization of an antiserum against the glucocorticoid receptor

An immunoglobulin (IgG) fraction from serum of a rabbit immunized with a highly purified preparation of glucocorticoid receptor from rat liver cytosol contained specific antibodies to glucocorticoid receptor. This was shown following incubation of the [³H]triamcinolone acetonide-glucocorticoid receptor (TA-GR) complex with the IgG fraction by (I) adsorption of the [³H]TA-GR-antibody complex to protein A linked to Sepharose, (II) an increased sedimentation rate of the [³H]TA-GR-antibody complex compared to that of the [³H]TA-GR complex, and (III) an increased molecular size of the [³H]TA-GR-antibody complex when compared to that of the [³H]TA-GR complex as judged from gel filtration. The antibody fraction was characterized with regard to titer, cross-reactivity and specificity. The antibodies cross-reacted with the glucocorticoid receptor from various rat tissues (liver, thymus and hippocampus), as well as with the glucocorticoid receptor from human normal lymphocytes, chronic lymphatic leukemia cells and human hippocampus. In the rat liver, the antibody bound to both the nuclear and the cytosolic glucocorticoid receptor (Stokes radius 6.1 nm). It did not cross-react with the proteolytic fragments of the glucocorticoid receptor, the 3.6 nm complex or the 1.9 nm complex. Binding of the antibodies was not seen to the androgen, estrogen or progestin receptors in rat to rat serum transcortin. With an indirect competitive ELISA (enzyme-linked immunosorbent assay) combined with various separation techniques, based on different physiocochemical principles, it was shown that the glucocorticoid receptor was the only detectable antibody binding protein from rat liver cytosol using this assay system. These findings also indicate an immunochemical similarity between glucocorticoid receptors in different tissues as well as in different species, but not between glucocorticoid receptors and other steroid hormone receptor proteins. The cytosolic and nuclear glucocorticoid receptors in rat liver were shown to be immunochemically similar.     

Evidence against a laminin receptor role for calsequestrin

Calsequestrin, a muscle calcium binding protein, has been shown to bind the extracellular matrix protein laminin and evidence has been presented that CAL (initially called aspartactin) is on the cell surface, consistent with a role as a laminin receptor (1). In this report, we present evidence that does not support a laminin receptor function for CAL. We found that CAL immunoreactivity could not be detected on live cultured chick myotubes unless they were permeabilized with detergent. Furthermore, polyclonal anti-CAL antibodies did not perturb myotube adhesion to laminin or the rate of myoblast fusion on laminin. Expression of the CAL cDNA in a melanoma cell line that was poorly adherent to laminin did not increase adhesion to laminin. In these cells, CAL could not be detected on the cell surface, and the majority of CAL was found to be secreted into the media.     

IgE antibody responses against Japanese cedar pollen in the mouse

IgE antibody responses against Japanese cedar pollen in the mouse were investigated to develop a mouse model of human allergy for combinations of factors including pollen administration routes, elicitation antigens and inbred mouse strains. Daily short term inhalation of native pollen or intratracheal administration of pollen suspended in saline induced IgE antibody responses in DBA/2, BDF1 and Balb/c mice, but failed to induce any detectable responses in C57BL/6 and C57BL/10 mice. Intraperitoneal injection of pollen suspension also induced IgE antibody responses in DBA/2, BDF1 and Balb/c mice but not in C57BL/6 mice. IgE antibody responses against pollen described above were detected by passive cutaneous anaphylaxis (PCA) reactions using crude extract of pollen as an elicitation antigen. On the other hand, IgE antibodies specific for antigen Sugi basic protein (AgSBP), which is a major allergen of pollen in humans (Yasueda, H., Yui, Shimizu, T., and Shida, T., 1983. Isolation and partial characterization of the major allergen from Japanese cedar (Cryptomeria japonica) pollen. J. Allergy Clin. Immunol. 71: 77-86), were also detected by PCA reactions using AgSBP in the sera from mice which received secondary or the tertiary stimulation by pollen. These results suggest that IgE antibody responses against Japanese cedar pollen in the mouse can be induced by airway sensitization and that the responses are genetically controlled by H-2-linked immune response genes. The results also suggest that not only IgE antibody responses specific for components other than AgSBP but also responses specific for AgSBP can be induced in the mouse by repeating appropriate sensitization by pollen.     

Production and characterization of a monoclonal antibody specific for the human lymphocyte low affinity receptor for IgE: CD 23 is a low affinity receptor for IgE

In the present study a gamma 1 kappa monoclonal antibody, Mab 25, specific for the receptor for the Fc fragment of IgE on lymphocytes (Fc epsilon RL) was established. This antibody was generated after fusion of spleen cells from mice immunized with the EBV-transformed lymphoblastoid cell line RPMI 8866, which is known to express Fc epsilon RL at high density. Mab 25 inhibits strongly the binding of IgE to RPMI 8866 cells and to other Fc epsilon RL-positive EBV-transformed lymphoblastoid cell lines. A 50% inhibition of IgE binding was observed at a Mab 25 concentration of 10 ng/ml. The binding of IgE was also inhibited by Fab fragments of Mab 25, suggesting that the inhibition is not simply due to steric hindrance or to an eventual binding through its Fc portion. Mab 25 only binds to cell lines expressing Fc epsilon RL. Mab 25 immunoprecipitated a single polypeptide with an apparent m.w. of 42 Kd, pI 4.9. The membrane molecule bound to and eluted from a Mab 25 immunoabsorbent had the same apparent m.w. and pI as the Fc epsilon RL purified from an IgE immunoabsorbent. Additionally, when RPMI 8866 cell lysates were cleared with Mab 25, no Fc epsilon RL could be bound to or eluted from an IgE immunoabsorbent. Mab 25 was found to weakly bind to a minor proportion of blood (1 to 4%), tonsil (2 to 9%) and spleen (4 to 5%) mononuclear cells with a low intensity. By double fluorescence analysis, most of the Fc epsilon RL-positive cells were found to be CD 20-positive B lymphocytes. The staining pattern of Mab 25 and the biochemical characteristics of the antigen detected by Mab 25 were comparable to those of the CD 23 Mab. The four CD 23 Mab MHM 6, PL 13, HD 50, and Tü 1 were found to inhibit the binding of IgE. PL 13 was found to totally inhibit the binding of Mab 25 to RPMI 8866 cells, whereas Tü 1 and MHM 6 only partially inhibited Mab 25 binding. HD 50 was unable to block the binding of Mab 25. The finding that different CD 23/Fc epsilon RL-specific monoclonal antibodies recognizing distinct epitopes have in common the capacity of inhibiting the binding of IgE suggests that upon binding they induce a conformational alteration of the Fc epsilon RL resulting in a loss of the IgE binding capacity. In conclusion, our data demonstrate that the CD 23 antigen is a low affinity receptor for IgE on lymphocytes.     

Characterization of a rabbit polyclonal antibody against threonine-AMPylation

An antibody against the posttranslational modification AMPylation was produced using a peptide corresponding to human Rac1 switch I region with AMPylated threonine-35 residue as an antigen. The resulting rabbit antiserum was tested for its abilities to recognize AMPylated proteins by western blot and immunoprecipitation. The antiserum is highly specific for threonine-AMPylated proteins and weakly recognizes tyrosine-AMPylated proteins. Depletion of serum with modified protein abolished its activity against tyrosine-AMPylated proteins. The antiserum also recognized native proteins with modification in an immunoprecipitation experiment. Interactions of the antiserum could be inhibited by competition with AMP but not with GMP or UMP. This antiserum had potential utility for the identification of unknown AMPylated proteins.     

IgE antibody against hepatitis B surface antigen in mice

Hepatitis B surface antigen (HBs antigen) was examined for elicitation of IgE production by injection into mice. The Prausnitz-Küstner (PK)-type skin test in the rat was employed for detection of IgE antibody to HBs antigen, because no sufficient purified HBs antigen was available as the challenging antigen for the passive cutaneous anaphylaxis (PCA) test in rats. The positive PK test was considered to be due to IgE antibody, since the active principle was inactivated by heating the sera at 56 C for 30 min, did not bind to protein A and was eliminated by anti-mouse IgE antisera. These data indicate that the PK-type test in rats can be used for detection of mouse IgE antibody when the amount of a test sample is not sufficient for the PCA test in rats.     

Binding of a mouse monoclonal IgE (anti-DNP) antibody to radio-derivatized polystyrene-DNP complexes

Polystyrene (PS) labware products (microtiter plates, test tubes, etc.) show radiation (gamma) dose-dependent carbodiimide (EDC)-mediated uptake of carboxyl-containing molecules such as DNP-[3H]Gly. The presence of water during irradiation increases, and oxygen decreases the coupling capacity of irradiated PS. The EDC-mediated attachment of DNP-Gly to PS is stable because it resists prolonged exposure to acids at low or high salt concentrations; the bond is sensitive to bases and oxidizing agents. Commercially available radiation-sterilized PS labware products also show elevated EDC-mediated uptake of DNP-[3H]Gly. Nonirradiated PS products or non-PS materials in these studies were inactive. Commercially irradiated PS microtiter plates were coated with DNP-amino acids in an EDC-mediated reaction, and the binding of a radiolabeled mouse monoclonal IgE (aDNP) to DNP-coated plates was studied. 1) The minimal ligand (DNP-Gly) and reagent (EDC) concentrations for plate coating to reach saturating antibody binding were found to be 0.2 mM and 0.2 mg/ml, respectively. High coating densities were suboptimal for antibody binding; 2) five to 60 min of coupling times yielded optimal coating densities; 3) The binding of antibody to DNP-Gly-coated plates reached half-maximal levels in approximately 40 min; 4) Dissociation of antibody from DNP-Gly and DNP-Ser-coated plates was very slow. Intra- and interassay coefficients of variation of antibody binding to plates coated with DNP-Gly under optimal conditions were generally below 3%. We conclude that the PS-bound DNP produced by this method is recognizable by anti-DNP antibodies. The optical quality of PS is not affected by radio-derivatization, and the ligand-coated plates obtained by these methods are suitable for colorimetric assays. All brands of heavily irradiated PS examined were suitable carriers for EDC-mediated coupling of DNP-aminoacids.     

The rabbit progesterone receptor. Evidence for a single steroid-binding subunit and characterization of receptor mRNA

Monoclonal antibodies were used to study the structure and the biosynthesis of the rabbit progesterone receptor. Proteins in nonfractionated uterine cytosol were submitted to gel electrophoresis in denaturing conditions, transferred onto nitrocellulose, and reacted with monoclonal antireceptor antibodies and 125I-protein A. A single 110,000-dalton protein was observed when precautions were taken during homogenization of the uteri and protease inhibitors used. Smaller forms of receptor (essentially of 79,000 daltons but also of 72,000 and in some experiments of 64,000 daltons) were present when these precautions were not observed and thus probably arose from artifactual proteolysis of receptor. When poly(A)+ RNA from rabbit uterus was translated in a reticulocyte lysate and the radioactive proteins precipitated by the antireceptor monoclonal antibodies, a radioactive protein of 110,000 daltons was also observed. Further evidence that this protein was the product of the translation of progesterone receptor mRNA was obtained by precipitation and immunoaffinity purification with several antireceptor monoclonal and polyclonal antibodies, inhibition of immunoprecipitation by purified receptor and its absence in a receptor-poor tissue (liver). Estrogen treatment is known to increase the concentration of progesterone receptor. RNA translation experiments showed that this effect is due to an increase in the concentration of receptor mRNA. The size of this messenger RNA was studied by sucrose gradient ultracentrifugation, followed by mRNA translation, and specific immunoprecipitation: progesterone receptor mRNA was found by this method to sediment at 20 S.     

Production of humanized antibody against human high-affinity IgE receptor in a serum-free culture of CHO cells, and purification of the Fab fragments.

We describe the preparation of Fab fragments of a humanized anti-human high-affinity IgE receptor (Fc epsilonRIalpha) antibody potentially useful for treatment of IgE-mediated allergic diseases. IgE-binding capacities of sixteen combinations of light and heavy chains of four recombinant anti-Fc epsilonRIalpha antibodies, chimeric CRA2, humanized CRA2, chimeric CRA4, and humanized CRA4, were compared. A combination in which both chains were of humanized CRA2 had the highest activity. Stable transfectant clones of four kinds of host cells expressing recombinant antibodies were established. CHO-K1 cells were the most productive. Serum-free media suitable for culture of the stable CHO-transfectant clones were screened. The concentration of the humanized CRA2, which the most productive clone secreted into the chosen serum-free medium, was approximately 100 microg/ml. A procedure for the purification of the antibody, papain-digestion, and purification of Fab fragments was established. The highly purified humanized Fab fragments are suitable for use to examine their in vivo activity and immunogenicity in primates.     

Characterization of a monoclonal antibody against the lymphoblast substance P receptor

A murine monoclonal antibody to the IM-9 lymphoblast substance P (SP) receptor has been produced which recognizes the membrane-associated proteins of the SP receptor as demonstrated by immunoprecipitation of [125I]SP affinity-labeled and [35S]methionine biosynthetically labeled IM-9 soluble membranes. SP and anti-SP receptor binding to [35S]methionine-labeled IM-9 cell proteins were directly compared by attachment of each to affinity supports. Eluants from these affinity columns were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and revealed an equivalent 33-kDa protein in both cases. This protein corresponds to one of the previously described [125I]SP specifically affinity-labeled membrane-associated proteins. In addition, two-color fluorescence-activated cell sorter analysis with human peripheral blood T lymphocytes with fluorescein-SP and rhodamine-labeled antireceptor antibody revealed a distinct population of cells (20 to 30%) that were equally labeled by both the fluorescent peptide and antibody. This result indicates that the anti-SP receptor antibody recognizes an epitope of the receptor that is common to both human peripheral blood T lymphocytes and IM-9 lymphoblast cells.