Use of an enzyme-linked immunosorbent assay (ELISA) for screening of hybridoma antibodies against cell surface antigens

Why recombinant antibodies - benefits and applications

Antibodies (Abs) are ubiquitous reagents for biological and biochemical research and are rapidly expanding into new therapeutic areas. They are one of the most important probes for determining how proteins function under normal and pathophysiological conditions. Abs are required for the quantification of targets, detection of temporal and spatial patterns of protein expression in cells and tissues, and identification of interacting partners and their biological activities. Their remarkable specificity and unique binding properties can facilitate three-dimensional structure determination using X-ray crystallography and electron cryomicroscopy. While hybridoma technology that involves animal immunization is often productive, many antigen targets do not generate useful Abs. This is particularly true if unique states of the target or critical non-immunogenic target sequences need to be recognized by the Abs. By using the methods of recombinant antibody generation, identification, and engineering, these 'hybridoma-refractory' antigens can be readily targeted. Specific, reproducible, and renewable recombinant Abs are proving to be invaluable reagents in applications ranging from biological discovery to structure determination of challenging macromolecules.

Binding specificity and internalization properties of an antibody-avidin fusion protein targeting the human transferrin receptor

The human transferrin receptor (hTfR1) is a membrane-bound protein involved in transferrin (Tf)-mediated iron uptake and is highly expressed on malignant cells. A second version of the receptor (hTfR2) also mediates Tf-dependent iron import. We previously developed a protein composed of avidin fused to a mouse/human chimeric IgG3 specific for hTfR (anti-hTfR IgG3-Av) that was originally designed to deliver biotinylated drugs into cancer cells. We have now found that anti-hTfR IgG3-Av does not cross-react with hTfR2 and binds hTfR1 expressed on the surface of cells, attached to a solid surface, and in solution. We also found that the hemochromatosis protein (HFE), another ligand of the TfR, does not inhibit the binding of anti-hTfR IgG3-Av to the receptor. In addition, using live cell laser scanning confocal microscopy (LCLSCM) we demonstrated that anti-hTfR IgG3-Av and anti-hTfR IgG3 are internalized into cells expressing hTfR1 at a similar rate. Furthermore, our proliferation and morphological studies demonstrated the effective cytotoxicity of a biotinylated toxin delivered by anti-hTfR IgG3-Av only into cells expressing hTfR1. Our results better define the properties of anti-hTfR IgG3-Av and pave the way for the rational design of future in vitro and in vivo studies for the treatment of human malignancies.

Tips and step-by-step protocol for the optimization of important factors affecting cellular enzyme-linked immunosorbent assay (CELISA)

CELISA, or cellular enzyme-linked immunosorbent assay, is a powerful and easy to use technique to study cell surface antigens under different stimulations. Nevertheless, some factors must be discussed and optimized prior to reaching a reproducible CELISA. These include the choice of cell density, fixative agent, blocking agent, culture medium, optimal antibody dilutions, and incubation time. In this paper, we first present a short review of some references devoted to CELISA by means of a comparison of these parameters, followed by their description. Then, we describe and study these different parameters using practical examples comparing TNF-induced ICAM-1 expression as an end point, on HBL melanoma and HUVEC. These cell lines were also chosen because they differ in their ability to grow as discontinuous and continuous layers, respectively. Furthermore, we designed a comprehensive flow chart, as well as a complete step-by-step protocol for CELISA optimization.

Modified flow cytometry and cell-ELISA methodology to detect HLA class I antigen processing machinery components in cytoplasm and endoplasmic reticulum

Flow cytometry and cell-enzyme linked immunosorbent assay (ELISA) are useful techniques for the quantitative analysis of cell surface antigen expression. Furthermore, flow cytometry can detect intracellular markers in cells permeabilized to facilitate the intracellular penetration of antibodies. However, to the best of our knowledge, neither method has been used to detect antigens located in the endoplasmic reticulum (ER) of cells. This limitation has a negative impact on the analysis of the expression of HLA class I antigen processing machinery components in cells. Therefore in this study, we show that markers located in cytoplasm and ER can be detected by flow cytometry and cell-ELISA in cells sequentially fixed with paraformaldehyde, heated in a microwave oven, permeabilized with saponin and reacted with monoclonal antibodies (mAb). Utilizing LMP10 as an intracytoplasmic marker and calreticulin and tapasin as ER luminal markers, we show that the modified flow cytometry and cell-ELISA are sensitive, simple and reproducible methods to detect HLA class I antigen processing machinery components in cells. Furthermore, testing of 10 human cell lines with HLA class I antigen processing machinery component-specific mAb has shown that the results obtained with the modified flow cytometry and cell-ELISA are significantly correlated. These results altogether indicate that the modified flow cytometry and cell-ELISA methods we have described will facilitate the analysis of the expression of HLA class I antigen processing machinery components in cells under physiological and pathological conditions. The resulting information will contribute to the characterization of the effect of changes in the expression of antigen processing machinery components on the recognition of cells by the host's immune system.

Whole cell ELISA for detection of tumor antigen expression in tumor samples

We have developed a whole cell enzyme-linked immunosorbent assay (ELISA) that detects the melanoma antigens gp100 and S-100 in tumor samples from patients with metastatic melanoma and the antigen CA 125 in tumor samples from patients with ovarian carcinoma. The assay is relatively simple to perform and interpret without specialized expertise in pathology. It is both sensitive and selective and is amenable to being automated. The results correlate very well with those obtained by flow cytometry and are in good accord with published values obtained by immunohistochemistry. We believe that this assay should be very helpful for characterizing autologous cell cancer vaccines and may also represent a useful alternative to immunohistochemistry for cancer diagnosis. It should be adaptable to other types of cancer where tumor antigens have been identified and good antibodies are available.

Reactivity of anti-erythrocyte antibody induced by Babesia gibsoni infection against aged erythrocytes

Effects of ageing treatment of erythrocytes to binding activity of the anti-erythrocyte antibody(s) in the serum of dogs infected artificially with Babesia gibsoni were examined by enzyme-linked immunosorbent assay (ELISA) using fixed cell antigen. When erythrocytes made senescent by two artificial ageing treatments, one of which was storing erythrocytes at 37 degrees C in medium for some days and the other was oxidation of erythrocytes with phenylhydrazine, reactivity of anti-erythrocyte antibody(s) in the infected serum to both types of treated erythrocytes was increased. These results suggest that such antibody(s) could play a role as one of the causes of anemia in canine babesiosis.

Growth suppression and astrocytic differentiation of glioma cells by interleukin-1

The effect of recombinant human interleukin-1 (rHuIL-1) derivatives on human glioma cell lines was examined in vitro. Five glioma cell lines, U-251 MG, U-373 MG, U-87 MG, A-172, and T98G, were incubated in medium containing 1% fetal calf serum and various concentrations of different type of rHuIL-1: OCT-43 (rHuIL-1 beta), OCT-7000 (rHuIL-1 alpha), and OCT-8000 (rHuIL-1 alpha). The high-affinity IL-1 receptors were expressed in the U-251 MG and U-373 MG cell lines, and rHuIL-1 was found to suppress cell growth and to induce morphological differentiation of these cell lines. Growth inhibition occurred in a dose-dependent manner in concentrations or rHuIL-1 ranging between 1 and 100 ng/ml. Interestingly, rHuIL-1 induced a transient growth of glioma cells shortly after administration, then suppressed cell growth with accompanying elongation of cytoplasmic processes. This unique process of transient growth stimulation followed by growth suppression was parallel to the efficacy of bromodeoxyuridine uptake in the rHuIL-1-treated cells. Concomitantly, accumulation of glial fibrillary acidic protein and cyclic adenosine monophosphate contents was observed in four glioma cell lines. Continuous rHuIL-1 treatment for longer than 30 days elicited irreversible astrocytic terminal differentiation. These results indicate that IL-1 is an effector on the growth regulation of glioma cells, resulting in astrocytic differentiation in vitro.

Anti-tumor antibody produced by human tumor-infiltrating and peripheral blood B lymphocytes

Cell suspensions from 69 human tumor biopsies and malignant effusions depleted of infiltrating T cells were incubated for 10-14 days with mitomycin-C-treated cells of the transformed T cell line MOT as feeder cells. B lymphocytes proliferated and differentiated as indicated by immunoglobulin (Ig) secretion in the culture supernatants (B cell expansion). Ig was present in culture supernatants of tumor cell suspensions incubated without MOT feeder cells (non-expanded cells), but the addition of MOT feeder cells to these cultures invariably resulted in a significant increase in Ig concentration. While IgG, IgA, and IgM isotypes were all detected in supernatants of both expanded- and non-expanded tumor cell suspensions, the increase in total Ig induced by MOT feeder cells was mainly due to an increase in IgG. Peripheral blood B lymphocytes (PBBL) from 15 cancer patients and 4 healthy individuals were also successfully expanded by the same method. In these it was shown that IgA was the predominant Ig isotype. Using a modified enzyme-linked immunosorbent assay, IgG of 25/36 expansions from tumor cell suspensions showed reactivity with autologous tumor targets, and that from 10/13 expansions reacted with allogeneic tumor targets of the same histological diagnosis. No reactivity was found against tumor targets of different histology. IgG of 4/10 expansions of PBBL from cancer patients showed reactivity with allogeneic tumor targets of the same histology, while no reactivity was demonstrated against tumor targets of different histology. IgG of expanded PBBL from healthy individuals showed no reactivity against tumor targets. This method allows detailed study of the specific humoral antitumor immune response of intratumoral and peripheral blood B lymphocytes in cancer.

Human monoclonal antibody [1-1-2D] against cancer of the uterine cervix

To obtain a human monoclonal antibody (h-MAb) against cancer of the uterine cervix, lymphocytes from the regional lymph nodes of 14 patients with cervical cancer were fused with a mouse-human heterohybridoma [II]. Of 6,419 hybridomas, 1,295 produced human immunoglobulins (IgG 670, IgM 737). We isolated clone [1-1-2D], which has produced human IgM with stability for more than a year. This antibody reacted with three of five cell lines of cervical cancer but not with normal fibroblasts. Histoimmunostaining showed positive responses to 9/15 specimens of cervical cancer and in 2/7 specimens from cases of cervical dysplasia. Most of the normal human and fetal tissues showed no positive immune response. The positive immune response of [1-1-2D] to the cell membrane observed by the fluorescence antibody method disappeared after periodate treatment and was weakened by trypsin. Neuraminidase did not affect immune reactivity. This antibody showed a positive response by the thin-layer chromatography immunostaining method and precipitated a glycoprotein having a molecular weight of 38 kD. These results suggested that the epitope of the [1-1-2D] antibody is present on a carbohydrate moiety not containing sialic acid that is carried on protein and lipid moieties.

A microELISA assay for detection of anti-HLA activity of mouse monoclonal antibodies using an Astroscan 2100 automated plate reader

A microenzyme-linked immunosorbent assay (microELISA) method has been developed using an Astroscan 2100 system automated plate reader which was initially designed for tissue typing by a two colour fluorescent microcytotoxicity assay. A 96-well plate ELISA used for screening mouse monoclonal antibodies raised against surface HLA antigens has been modified for use with the Astroscan plate reader and 72-well typing trays. The existing substrate 4-methylumbelliferyl-beta-D-galactoside (4MUG) has been replaced with fluorescein-di-beta-D-galactopyranoside (FDG), to provide a wavelength (530 nm) detectable by the Astroscan or other automated plate readers designed for reading microcytotoxicity assay plates. The assay volumes have also been reduced tenfold for use with Terasaki microtest plates. The assay now has the major advantage of requiring only 5 microliters of test supernatant allowing hybridomas to be screened earlier during a fusion and on a wider cell panel. The use of the large panel which includes B lymphoblastoid cell lines (B-LCL) and mouse L cell transfectants expressing HLA genes, reduces the length of time the hybridomas need to be kept in tissue culture before selection. Other advantages include the reduction in the number of target cells required, smaller volumes of reagents throughout the assay and the ability to screen cytotoxic as well as non-cytotoxic monoclonal antibodies. The sensitivity of this microELISA proved to be comparable with the original assay and so provides an efficient screening method for monoclonal antibodies.

Human antiglioma monoclonal antibodies from patients with astrocytic tumors

The current management of malignant gliomas is unsatisfactory compared to that of other solid tumors; the expected median survival period is less than 1 year with the patient undergoing conventional surgery, radiotherapy, and chemotherapy treatment. Immunological reagents could be a useful adjunct. Human monoclonal antibodies derived from patients with astrocytic tumors might recognize subtle antigenic specificities that would differ from those recognized by xenogeneic (murine) systems. Five hybridomas, designated as BT27/1A2, BT27/2A3, BT32/A6, BT34/A5, and BT54/B8, were produced from the fusion of peripheral blood lymphocytes of four patients with astrocytic tumors to the human myeloma-like cell line TM-H2-SP2. This cell line has a 46, XX karyotype and is negative for hypoxanthine guanine phosphoribosyltransferase. All five human monoclonal antibodies produced 2.4 to 44 micrograms/ml of immunoglobulin M, had a similar but not identical pattern of reactivity against a panel of human tumor cell lines, and failed to react with normal human astrocytes. Labeling of four neuroectodermal tumor explant cultures by BT27/2A3 was demonstrated by flow cytometry. Karyotyping of three of the five hybridomas demonstrated that two were pseudodiploid (2-3n) and one hypodiploid (less than 2n). The monoclonality of the hybridomas was evaluated by Southern blot analysis of JH gene rearrangements, revealing two types of rearrangements for each hybridoma, both consistent with monoclonality. Preliminary antigen characterization indicated that at least four of the five human monoclonal antibodies were directed to cell-surface glycolipids.

Novel antigens characteristic of neuroendocrine malignancies

The authors describe the immunochemical detection, biochemical characterization, and tissue distribution of neuroendocrine antigens recognized by three newly developed monoclonal antibodies (MoAb) obtained after immunization of mice with the variant small cell lung cancer (SCLC) cell line NCI-H82. RNL-1 was reactive with neuroendocrine tissues similar to the SCLC cluster-1 MoAb, known to recognize N-CAM. Antibodies RNL-2 and RNL-3 are directed against different epitopes on the same proteinaceous complex. Both MoAb recognize an intracellularly located, water-soluble antigen which has a subunit composition with a protein triplet ranging in molecular weight between 44 and 45 kilodaltons (kD) next to a component of approximately 30 kD. The antibodies RNL-2 and RNL-3 reacted with a subset of neuroendocrine tissues and neuroendocrine neoplasms. In lung cancer both antibodies reacted only with some SCLC and carcinoids and not with nonneuroendocrine lung carcinomas. The potential diagnostic applicability of antibodies RNL-1, RNL-2, and RNL-3 is discussed.

A simplified cellular ELISA (CELISA) for the detection of antibodies reacting with cell-surface antigens

This paper describes the adaptation of a cellular enzyme-linked immunosorbent assay (CELISA) for the detection of antibodies to cell-surface antigens. This CELISA has the advantages of convenience and rapidity and is therefore ideally suited for the screening of a large number of hybridoma culture supernatants. The basic procedure involves the direct drying of cell suspensions onto the wells of enzyme immunoassay (EIA) plates and a subsequent EIA with appropriate blocking reagents. In order to overcome high background binding of primary antibodies to Fc receptors and of secondary antibodies to surface Ig (sIg), this method involves a blocking step consisting of unlabelled secondary antibodies. Once CELISA plates are prepared, they can be stored for a period of at least 6 months and hence this assay does not rely on the availability of fresh, viable cells for each assay. This assay is simple, reproducible and sensitive. The results can be assessed in an objective manner and can also be adapted for the detection of cellular antigens. This paper describes a CELISA for the detection of antibodies to blood group antigens and human leukocyte (HLA) antigens.

A method for blocking antigen-independent binding of human IgM to frozen tissue sections when screening human hybridoma antibodies

Using an indirect immunoperoxidase technique antigen independent binding of both human monoclonal and polyclonal IgM was found to a wide range of frozen sections of normal and malignant human glandular epithelia. Identical binding was found using dimeric human IgA (dIgA), whereas no binding was found with monomeric human IgA or human IgG. Secretory component (SC) was found to be the component in these tissues mediating antigen-independent binding of human IgM and dIgA antibodies. A method for the blocking of this antigen-independent binding of human IgM and dIgA was evaluated. Frozen sections of tissues containing SC were blocked with antibody to endogenous immunoglobulin and preincubated with rabbit anti-secretory component antibody (anti-SC) before applying the human monoclonal antibody. This treatment blocked the binding of control polyclonal and monoclonal human IgM to sections of SC-containing tissues such as respiratory and colonic epithelia. The influence of anti-SC on the binding of dIgA could not be established due to interactions between the anti-SC antibody and the IgA preparation. Using this method human hybridoma supernatants containing IgM could be readily screened for reactivity with frozen tissue sections from patients with colo-rectal cancer. This approach is recommended for the screening of human IgM monoclonal antibodies on frozen human tissue sections.

Human-human hybridoma producing monoclonal antibodies against colorectal cancer-associated antigens

Lymphocytes from lymph nodes draining the tumor region in patients with colorectal cancer were fused with two different human B-lymphoblastoid cell lines, LICR-LON-HMy-2 (HMy-2) and WI-L2-729-HF2 (729-HF2), to generate hybridomas synthesizing antibodies reacting with tumor-associated antigens. In this way 220 hybridomas were obtained which produce antibody reacting with colon cancer cells. All established clones produced IgM. Four human monoclonal antibodies have been further analyzed. The cell lines producing these antibodies are all hybrids based on DNA analysis. Three of the antibodies (G4146, B9165 and D4213) showed binding to differentiation antigens by immunocytochemical analysis on different cancer cell lines and normal human leucocytes and by immunohistochemical analysis on sections of frozen malignant and normal tissues, while the fourth (F11348) showed a reaction with all cells and tissues tested. Western blots of tumor extracts showed binding of G4146 to two components from colon cancer cells with Mr of 59 K and 61 K, while B9165 bound to a 43 K component and F11348 to several components with Mr from 30 to 200K. D4213 showed no binding in this analysis. The results obtained demonstrate the successful application of hybridoma technology to produce human monoclonals with reactivity to differentiation antigens.

Detection and identification of HLA antigens in dried spleens by means of enzyme linked immunosorbent assay (ELISA)

HLA class-I and class-II antigens were detected in extracts of dry spleen tissue allowed to age from 1 to 17 months, using monomorphic anti HLA monoclonal antibodies and the ELISA technique. Using polymorphic HLA alloantisera samples of spleen tissue could be characterized and differentiated. The potential use of dried tissues and blood stains is discussed.

Monoclonal antibodies to ROS 17/2.8 cells recognize antigens, some of which are restricted to osteoblasts and chondrocytes

We have raised a panel of 15 monoclonal antibodies (MAbs) recognizing cell surface antigens of the rat osteoblast-like cell line ROS 17/2.8. The MAbs were selected on the basis of preferential binding to ROS 17/2.8 cells compared to ROS 25/1 cells. Immunohistochemical studies of antigen localization on cryostat sections of rat calvaria, long bone, and soft tissues demonstrated that five of these MAbs, UBIM 1, 2, 3, 12, and 17, recognize antigens that are restricted to normal rat osteoblasts and chondrocytes. The antigens appear to be localized to the cell surface of the osteoblast, with no apparent staining of bone matrix in either undecalcified or decalcified sections. In vitro, these MAbs recognize cell surface antigens present on two additional cell lines, ROS 24/1 and Rat 2 cells, and on the adherent cell population cultured from rat long bone marrow. Of these MAbs, three (UBIM 1, 2, and 3) recognize high-molecular-weight antigens of Mr 200,000-225,000. This study has also identified cell surface antigens of ROS 17/2.8 cells that are not expressed by osteoblasts in vivo. MAbs UBIM 9 and 21 bind to marrow cells in long bone sections, to the 7-day-old nonadherent cell population from cultured marrow, and to lymphoid tissue in sections of spleen. Another four MAbs (UBIM 10, 11, 14, and 22) bind to a variety of cells and tissues both in vitro and in vivo. Studies of the interactions of this panel of MAbs with osteogenic tissues and cell lines may have an important impact on the understanding of osteoblast physiology.

Human monoclonal autoantibodies produced by hybridomas derived from lymphocytes of multiple sclerosis patients

The aim of this study was to characterize autoantibodies produced in vitro by peripheral blood lymphocytes (PBL) of patients affected with multiple sclerosis (MS). We studied supernatants from man-mouse hybridomas established by fusion of PBL from 6 MS patients (group I) and from 13 individuals free of any neurological pathology (group II) with the mouse myeloma cell line P3X63 Ag8-653. They were screened for human IgG or IgM production by ELISA. Autoantibody activity against lymphocytes was studied by cell-binding ELISA. Anti-tissue reactivity was assessed by indirect immunofluorescence assay (IFA) on human cerebellum and peripheral nerve as well as on a panel of 8 non-nervous tissues. Additional ELISA tests were performed on 4 purified cellular antigens. Among 522 supernatants in group I, 13.7% contained Ig, mainly IgM, as compared to 25% among 1212 supernatants in group II; 8.3% in group I and 6.7% in group II contained anti-tissue autoantibodies. Antibodies against purified cellular antigens were found in 6% of the supernatants in group II versus 7% in group II. One human monoclonal anti-astrocyte antibody from group I was further studied. This IgM lambda (SAN-7) was particularly polyreactive and recognized glial fibrillar acid protein and other intermediate filaments, as well as tubulin and myosin. Moreover, cross-reactivity was observed with a hapten (TNP-BSA).

Characterization of a method using viable human target cells as the solid phase in a cell concentration fluorescence immunoassay (CCFIA) for screening of monoclonal antibodies and hybridoma supernatants

A new method has been characterized for the use of viable target cells as the solid phase for screening of hybridoma supernatants in a cell concentration fluorescence immunoassay (CCFIA). Briefly, the specific target antigen on the cells is bound by the monoclonal antibodies and revealed by use of a fluoresceinated second antibody. Separation of free from bound antibody is accomplished by filtration in the 0.2 micron filter-bottom wells of specialized assay plates. Processing is automated in a Pandex screen machine, resulting in numerical fluorescence values for each well. This method is rapid (under 1 h per 96-well plate), highly sensitive (down to 0.2 ng/ml) and sparing of target cells (0.3-2.5 X 10(4) cells per assay well). It has been applied to 37 different varieties of human solid tumor cells, as well as to human peripheral blood mononuclear cells. The cells used as targets for the characterization of this method were still capable of attachment and growth when recovered post-assay. This method was compared with a viable cell enzyme-linked immunosorbent assay (ELISA) method, showing similar sensitivity and greatly shortened assay time. Comparison of the results from this method with those obtained from flow cytometric analysis performed on viable cells showed close correlation, whereas a lower correlation was seen with immunohistochemical methods using acetone-fixed cells. Development of this method made it possible to rapidly screen many thousands of hybridoma supernatants and successfully select those which were specific for surface antigens on viable cells.

A solid-phase immunoassay to screen anti-HLA monoclonal antibodies

A solid-phase assay to detect anti-HLA monoclonal antibodies was developed. In this assay microtiter plates are coated with antigens solubilized from cultured lymphoid cells by sonication and then incubated with anti-HLA monoclonal antibodies. The antigen-antibody interaction is indicated by the development of color following the addition of peroxidase-conjugated anti-mouse Ig xenoantibodies and its substrate. The assay is rapid since it does not require centrifugations during the washing steps. Furthermore the assay is simple, reproducible and suitable to screen large numbers of samples and to detect antibodies recognizing determinants not exposed on the membrane of viable cells. The sensitivity of the assay is influenced by the pH of the buffer used to coat plates with antigens, by the number of cells used to prepare soluble antigens, by the incubation time of antigen preparations with plates and by the incubation time of antibody preparations with antigen-coated plates. Titration of anti-HLA monoclonal antibodies with known specificity and screening of hybridomas generated with splenocytes from mice immunized with cultured human lymphoid cells indicate that the sensitivity of the solid-phase assay is similar to that of the ELISA with lymphoid cells.

T lymphocyte development in horses. I. Characterization of monoclonal antibodies identifying three stages of T lymphocyte differentiation

Six monoclonal antibodies reacting with equine T lymphocytes at different stages of maturation were selected from antibodies produced against lymphoid cell preparations. EqT12 and EqT13 antibodies identified subsets of cortical thymocytes with high terminal deoxynucleotidyltransferase (TdT) activity and no phytolectin responsiveness. EqT12+ thymocytes were scattered throughout the cortex while EqT13+ thymocytes were located in the subcapsular cortex. EqT12 bound to small numbers of bone marrow cells, splenocytes, and circulating lymphoid cells, but not to mature T lymphocytes. EqT13 bound to very small numbers of bone marrow cells but not to more mature lymphocytes. EqT6 and EqT7 reacted with a large population of cortical thymocytes with high TdT activity and no phytolectin responsiveness. EqT2 and EqT3 bound primarily to medullary thymocytes with low TdT activity. Eq2+ thymocytes responded to phytolectin stimulation while EqT3+ thymocytes did not. EqT2 and EqT3 bound to 33% and 91% of circulating T lymphocytes, respectively. The T lymphocytes bound by both antibodies included cells capable of suppressing a mixed lymphocyte reaction. Thus, EqT12 and EqT13 identify cells with the functional characteristics of prothymocytes. EqT6 and EqT7 identify resident cortical thymocytes, and EqT2 and EqT3 identify a subpopulation of mature T lymphocytes and all mature T lymphocytes, respectively.

Characterization of monoclonal antibodies to protoplast membranes of Nicotiana tabacum identified by an enzyme-linked immunosorbent assay

Murine monoclonal antibodies to protoplast membrne antigens were generated using mouse myelomas and spleen cells from mice immunized with Nicotiana tabacum L. leaf protoplasts. For selecting antibody-secreting clones, a sensitive and rapid enzyme-linked immunosorbent assay (ELISA) for monoclonal antibody binding to immobilized cellular membrane preparations or immobilized protoplasts was developed. With intact protoplasts as immobilized antigen, the ELISA is selective for antibodies that bind to plasma-membrane epitopes present on the external surface of protoplasts. Using the membrane ELISA, a total of 24 hybridoma lines were identified that secreted antibodies to plant membrane epitopes. The protoplast ELISA and subsequent immunofluorescence studies identified four hybridoma lines as secreting antibodies which bound to the external surface of protoplasts and cells. The corresponding antigens were not species- or tissue-specific, were periodatesensitive, and were located in membranes which equilibrated broadly throughout a linear sucrose gradient. When protein blots of electrophoretically separated membrane proteins were probed with these antibodies, a band of Mr 14 kilodaltons (kDa) and a smear of bands of Mr 45-120 kDa were labeled. An additional set of three antibodies appeared by immunofluorescence to bind to the plasma membrane of broken but not intact protoplasts and labeled membranes equilibrating at a density of approx. 1.12 kg·l(-1) in a linear sucrose density gradient. These classes of monoclonal antibodies enlarge the library of monoclonal antibodies (Norman et al. 1986, Planta 167, 452-459) available for the study of plant plasma-membrane structure and function.

Identification and characterization of an antigen specific for normal erythroid precursor cells and its application in diagnosis of erythroleukemia

A monoclonal antibody (designated K:1-6F) generated by hybridization of mouse myeloma cells with spleen cells from mice immunized with the erythroleukemic cell line K562 was found by fluorescence-activated cell sorter analysis, dot-blot assay and electroimmunoblotting to bind to a majority of cells in the K562 and HEL erythroleukemic cell lines, to a subset of cells of the erythroid lineage from normal bone marrow, to a subset of cells in all analysed cases (total 10) of erythroleukemia, and weakly to cells from patients with myeloid leukemia. The antibody did not bind to normal erythrocytes, monocytes, T- and B lymphocytes or granulocytes, as well as a panel of human malignant cell lines of hemopoietic origin (HL60, U937, Daudi, Molt-3, RH-L4 and U266). Biochemical characterization of the antigen defined by the antibody suggests that eht epitope is defined by a carbohydrate structure alone or in combination with proteins. Four molecules with Mr 100 kD, 65 kD, 45 kD and 18 kD respectively were immunoprecipitated from Triton X-100 extract of K562 erythroleukemia cells. Neuraminidase did not affect the binding of the antibody, whereas tunicamycin reduced the K:1-6F expression. The K:1-6F Mab was in normal bone marrow found to be specific for erythroid precursor cells and may therefore be useful in examination of normal and leukemic erythropoiesis.

Generation and characterization of a monoclonal antibody (1C5) to human migration inhibitory factor (MIF)

A monoclonal antibody was raised in mice against human MIF of the Mr 14,000 kd, produced by Concanavalin A-stimulated peripheral blood mononuclear cells. A hybridoma (1C5) secreting an IgG 1 antibody was selected which binds, yet does not neutralize MIF in the macrophage migration assay. MIF activity may be released from immobilized antibodies by acidic buffer elution. The eluate consists of three major bands at Mr 8,000, 14,000 and 28,000 as revealed by SDS-polyacrylamide gel electrophoresis and molecular sieve chromatography (HPLC). By radioimmunoassay and enzyme-linked immunoassay, it could be shown that the antibody binds material with isoelectric points of 4.5 to 5.0 and of 3.0, which coincides precisely with the biological activities. Similar congruencies between the distribution of biologically reactive and binding material were found in molecular sieve and ion exchange chromatography. It is concluded that the antibody 1C5 reacts with most molecular weight entities of MIF which seem to be structurally related and which display similar characteristics as described for guinea pig and mouse MIF.

Glutaraldehyde fixation of target cells to plastic for ELISA assays of monoclonal anti-HLA antibodies produces artefacts

We found that an ELISA method for screening mouse monoclonal antibodies raised against antigens of the HLA system, that involves glutaraldehyde fixation of the target cells, produces both false negatives and false positives. The false negative results are due to destruction and/or modification of the antigenicity of some HLA-D region coded molecules; the false positives are mostly caused by non-specific adhesion of IgM, even at 1.625 micrograms/ml, to glutaraldehyde fixed cells. To a lesser extent there is nonspecific binding of IgG2a and IgG2b monoclonal antibodies particularly at concentrations above 12.5 micrograms/ml. These findings are unfortunate because the fixation of cells to the plates appeared to be a major technical advance as it removed the need for multiple centrifugation steps in the ELISA assay.

Human-human hybridomas for the study of anti-tumor immune response in patients with colorectal cancer

Human-human hybridoma technology was evaluated for the study of humoral immune reactions of colorectal cancer patients against their own tumors. Six fusions were carried out with lymphocytes from mesenteric lymph nodes from patients with colorectal cancer, using the human B-lymphoma cell line LICR-LON-HMy-2 as fusion partner. A total of 294 wells with cell growth were obtained. Supernatants from 26 of these reacted in enzyme-linked immuno-sorbent assay (ELISA) with one or more colon cancer cell lines. Cells from only one of these wells (D 4213) could be cloned. The clone was shown to produce antibody which by immunocytochemical analysis reacted with a panel of colon cancer cell lines and melanoma cell lines but not with several other cancer cell lines or normal human leukocytes. By immunohistochemical analysis on formalin-fixed paraffin-embedded tissue this antibody reacted strongly with antigen expressed by autologous and allogeneic colorectal cancers. Faint staining could occasionally be observed on normal colon epithelium. D4213 is a hybrid cell line since it is tetraploid and produces kappa and lambda light chains as well as gamma and mu chains, whereas HMy-2 produces only kappa and gamma chains. The study produces only kappa and gamma chains. The study suggests that patients may possess B cells producing antibody reactive with their own malignant cells.

Description and comparison of three in vitro methods for the detection of guinea pig MHC antigens

Two methods (an immunoenzymatic and a cell dot immunobinding assay) are described and compared with a reference protein A rosetting assay, for the detection of guinea pig class I and class II histocompatibility antigens. The main requirement of these three assays for obtaining good results is the use of whole fresh target cells since all tested experimental conditions for fixing cellular antigens (glutaraldehyde, formaldehyde, paraformaldehyde), as well as for obtaining cell monolayers (adherence, desiccation, poly-L-lysine) presented several drawbacks and were unsuccessful in our hands. The comparison between the three methods shows that the immunoenzymatic assay gives good results but that it is less reproducible than the other two. The cell dot immunobinding is highly sensitive, reproducible and economical. It can be used for genetic typing and alloantigen analysis of guinea-pig lines, instead of the rosetting method, which is highly reliable but time consuming.

Interaction of monoclonal antibodies with the IgE-receptor on rat mast cells and rat basophilic leukemia (RBL) cells

The close relation between rat mast cells and rat basophilic leukemia (RBL) cells with regard to the presence of receptors for IgE and Fc gamma led us to generate monoclonal antibodies directed against cell surface antigens. Hybridomas were obtained by the fusion of NS1 mouse myeloma cells with murine spleen and lymph node cells. The culture supernatants were assayed by two ELISA techniques: a) for the production of mouse immunoglobulin in general and b) for antibodies directed against surface antigens of RBL cells. For this purpose RBL cells were attached to polyvinyl chloride microtitre plates. Eight hybrids produced antibodies directed against surface antigens on RBL cells. Hybrids were cloned and characterized with regard to their isotype and light chains. All eight clones secreted IgM with K light chains. Immunofluorescence studies performed with RBL cells revealed that all eight antibodies were able to show a specific fluorescence. Furthermore, four of these eight antibodies also showed a specific fluorescence with purified rat mast cells. These four antibodies were analyzed as to their ability of interacting with the IgE-receptor on RBL cells and purified rat mast cells. They reduced the binding rate of radiolabelled rat IgE to RBL and rat mast cells. A mutual inhibition of the passive cutaneous anaphylaxis (PCA) reaction in the rat by either mixing mouse reaginic serum directed against 2,4-dinitrophenol bovine serum albumin (DNP-BSA) or by mixing monoclonal mouse anti-DNP IgE with the monoclonal mouse anti-cell surface (rat basophilic leukemia, rat mast cell) IgM was determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of monoclonal antibodies raised against the prostatic cancer cell line PC-82

For production of monoclonal antibodies (McAbs), hybrid cells were prepared by fusion of spleen cells of BALB/c mice immunized with the human prostatic cancer cell line PC-82 and the P3-X6(3)Ag8.653 murine myeloma cell line. Supernatants of approximately 500 hybrid clones were screened for prostate specific antibodies using an ELISA on PC-82 cells. A selection of antibodies was further tested for their specificity on a large series of different tissues. A broad cross reactivity pattern was obtained. Most cross reactivity was with pancreatic tissue, kidney, and bowel. One antibody turned out to react with prostate stromal cells. Two McAbs (ER-Pr 1 and ER-Pr 2) reacted solely with prostatic epithelium. Monoclonal antibody affinity chromatography combined with SDS-PAGE showed that both antibodies were directed against a 35-kD protein. Immunoblotting revealed that this protein is identical to prostatic antigen (PA). The epitope detected by ER-Pr 1 and ER-Pr 2 was largely preserved after formalin-fixation of prostatic tissues which renders these antibodies very suitable for routine examination of tissue sections.

The generation of monoclonal antibodies against human pancreatic exocrine cancer: a study of six different immunisation regimes

Six different immunisation regimes have been used to generate spleen cells with reactivity against human pancreatic exocrine cancer. Immunised spleen cells were fused with an NSO/1 myeloma line and supernatants from these hybridomas selectively screened for monoclonal antibodies which bound predominantly to a pancreatic cancer cell line (GER). The spleen cells from hairy litter mates immunised with pancreatic cancer xenograft homogenates and viable GER cells generated 13% of hybridoma supernatants which showed some selectivity for GER pancreatic cancer cells in a fixed cell ELISA assay. The other methods produced only 4% of hybrids with selectivity for GER cells. The antigen distribution on gluteraldehyde fixed cells was similar to that found for viable cell monolayers but many antigens were unstable on formalin fixation. Immunohistochemical staining of GER cells grown on glass slides showed a heterogeneity of antigen distribution with up to 70% of the cells exhibiting a vesicular pattern of staining. Fifty percent of the antibodies which bound to GER cells were also reactive against antigens in formalin-fixed paraffin-embedded tissue sections of the original GER tumour. Monoclonal antibody DD9E7 identified an antigen expressed on 12/14 pancreatic adenocarcinomas. The antibody showed strong staining of malignant luminal membranes and cytoplasm. The antigen was also present in normal salivary and sweat glands, and colon and breast carcinomas, but its tissue distribution was unlike that of CEA or EMA. The expression of this antigen in 12/14 of pancreatic carcinomas suggests that DD9E7 may be a useful reagent for pancreatic tumour detection.

Specificities and binding properties of 2 monoclonal antibodies against carcinoma cells of the human urinary bladder

Mice were immunized with cultured cells derived from transitional cell carcinoma of the human urinary bladder (TCC). Spleen cells were fused with mouse myeloma cell line Sp2/0-Ag14 and the hybridomas obtained screened for antibody production against a panel of human cells. Two hybridomas were selected for further studies. The antibodies from one of these hybridomas (P7A5-4) could clearly discriminate between malignant and normal cells from the bladder, both when tested with cultured cells and fresh tissue. The P7A5-4 antibodies, however, also reacted with some non-TCC cultured carcinoma and melanoma cells but to a lesser extent. This difference in reactivity was even more pronounced in the fresh tumours tested, thus indicating a quantitative difference in antigen expression between TCC and other cells. From extracts of TCC cells, P7A5-4 bound three polypeptides of mol. wts 92Kd (ConA+), 23 and 17Kd (ConA-). The antibody derived from hybridoma SK4H-12 bound a ConA reactive glycopeptide of 100Kd mol. wt, the expression of which was almost entirely restricted to urothelial cell lines and tissue of TCC origin, as shown by immunocytochemical studies. The finding in this study of new antigens associated with urinary bladder carcinoma, extend the results obtained previously in our laboratory (Koho et al., 1984; Paulie et al., 1984) and further delineate the heterogeneity of tumour-associated antigens in this human tumour system.

A tumor-associated antigen expressed in melanoma cells with lower malignant potential

The antigen K-1-2, detectable by a MAb is found in nevi and melanomas. It is associated with melanoma cells of low invasive and metastatic potential as shown by immunoperoxidase studies with cell lines, biopsies and autopsies: K-1-2 occurs in melanoma cell line SK-Mel 25, but not in cell line A-375. A-375 has a higher malignant potential than SK-Mel 25 because, in contrast to SK-Mel 25, it produces plasminogen activator and grows in nude mice. K-1-2 was frequently strongly expressed (greater than or equal to 50% cells positive) in flat (less than 1.5 mm) and less frequently in medium and thick primary tumors. In thick primary melanomas K-1-2 positive cells were confined to the junctional zone or to marginal, flat areas of the tumor. Only rarely does K-1-2 occur in metastases. Strong expression of the K-1-2 antigen was found less often in primary melanomas, which develop early metastases, than in tumors that had not metastasized during an observation period of 18 months. In 5 patients with disseminated metastatic disease, metastases strongly expressing K-1-2 and those negative for this marker or containing only a minor percentage of K-1-2 positive cells were observed simultaneously or at different times. These findings suggest that a change from high malignancy to low malignancy--as observed in animal systems--may also occur in human melanoma.

Detection of antibodies to cell surface antigens by a simplified cellular ELISA (CELISA)

An improved method for screening human hybridoma antibodies to cell surface antigens is described. The following modifications have been developed: rapid expansion of desired screening cell types by EBV transformation; use of only 5 X 10(4) cells/well; elimination of the need for glutaraldehyde fixation; elimination of the requirement for PLL to attach cells to microplates; preparation of a large number of plates which can be stored at 4 degrees for 3 months; Protein A-peroxidase ELISA assay yielding excellent replicates, low background "noise", and high OD readings for positive wells. The techniques we have developed should greatly simplify and shorten the assay procedures for detecting human antibodies to a variety of cell surface antigens.

A cell surface ELISA in the mouse using only poly-L-lysine as cell fixative

An ELISA using plates coated with mouse spleen cells has been developed for analysis of antibodies to cell surface antigens. Such assays have been used extensively with human cells or with tumor cells in various species, but application to normal mouse lymphocytes has been limited. Use of normal spleen cells allows access to the genetic resources offered by recombinant, congenic, and mutant mouse strains, in the preparation of cell-coated ELISA plates, the use of glutaraldehyde was found to be unnecessary and it was eliminated, thereby avoiding the destruction of some cell surface determinants. Poly-L-lysine, which was used to treat plates, was found to provide sufficient adherence and preservation of the cells. Binding of biotinylated monoclonal antibodies to cells could be detected at approximately 10 ng/well. In inhibition assays, unlabeled antibodies could be detected at approximately 10 ng/well. Cell-coated plates are stable once prepared, and can be stored for months before use. The assay described can be used to quantitate levels of antibody to a particular epitope, and can also be adapted for screening of fusions for monoclonal antibodies to cell surface antigens.

A monoclonal antibody (NAT-9 II:3F-6F) that identifies a differentiation antigen on human myeloid cells

A monoclonal antibody, designated NAT-9 II:3F-6F (IgM), was generated by hybridization of mouse myeloma cells with spleen cell from mice immunized with normal human bone marrow cells. The antibody reacted with 40-60% of bone marrow cells as analysed on samples from 40 normal individuals and only with a subpopulation of human acute myeloid leukemia (AML) cells of the M2 class (20/20 tested) and M4 class (12/12 tested) (subclasses of the French-American-British (FAB) classification), but not with leukemic cells of the M1 (0/12 tested) and M5 (0/12 tested) FAB subclasses. This is in contrast to many other myeloid-specific monoclonal antibodies. Fluorescence-activated cell sorter (FACS) analyses and morphological examination of cells stained with peroxidase as based on the NAT-9 II:3F-6F monoclonal antibody showed that this antibody reacted with a distant differentiation antigen which is absent on myeloblasts, but expressed on promyelocytes, myelocytes, metamyelocytes, band neutrophils, and on a minority of mature granulocytes. NAT-9 II:3F-6F did not bind to circulating monocytes, T and B cells, erythrocytes and a variety of different human cell culture lines. Immunoblotting demonstrated that the antibody bind to a cellular component with a Mr approximately 97.400 dalton. The antibody may be useful in immunological subclassification of non-lymphoid leukemias and in studies on hematopoiesis.

Antigens differentially expressed on surface and cytoplasmic structures of human myeloid cells

Specialized internal granules are a major feature of myeloid differentiation and are deficient in most acute myeloid leukemia cells. Although they arise from the same synthetic apparatus as does the plasma membrane, their relationship to it is not well characterized in human tissues. Using murine monoclonal antibodies, we have identified myeloid-related structures that illustrate three possible modes of antigen expression in these organelles. Immunocytochemical studies with the light microscope have shown that the first (D51) was restricted to the surface of neutrophils, monocytes, megakaryocytes and platelets; a second (D46) was found on the surface of blastic cell lines but on only internal components of mature granulocytes; the third (H36/71) appeared on both the surface and internal particles of promyelocytes, myelocytes and polymorphs. These model antigens may be used to study the control of granule synthesis in normal and leukemic cells.

Monoclonal antibody against tumour-derived cell line shows heterogeneity of altered hepatocytes during AFB1-induced carcinogenesis

Monoclonal antibodies have been raised against a tumour cell line (JB1) derived from an aflatoxin B1-fed rat liver. One antibody MRC TU/J1 has been characterized in terms of its immunohistochemical staining in sections of control and AFB1-fed liver and by the proteins which it immunoprecipitated. The antibody reacted with bile duct epithelium in all sections. In control liver sections there was staining of hepatocyte membranes, with increased stain in periportal regions in animals greater than or equal to 12 weeks old. In AFB1-fed liver sections, areas of biliary hyperplasia were stained and after 4 weeks on AFB1-diet, foci of altered hepatocytes were visible. These were negative, positive or heterogeneous with respect to antibody stain. The antibody reacted much more strongly with adenomatous and cholangiomatous tissue compared with trabecular regions of hepatic tumours which developed in animals after 14 weeks on AFB1 diet and 9 months on control diet. After immunoprecipitation of 14C-leucine-labelled proteins from a JB1 cell lysate by MRC TU/J1, 5 bands in the molecular weight range 43,000-49,000 daltons were visualized on 10% SDS-PAGE gels. A similar result was obtained with 14C-glucosamine in place of leucine, indicating that all 5 bands were glycoproteins. Deglycosylation of JB1 cell lysates with CNBH3-/IO(4)- prevented immunoprecipitation of all bands, suggesting that MRC TU/J1 recognized antigenic sites on the carbohydrate portions of the molecules.

Characterization of antibodies to a placenta-specific antigen cross-reacting with a choriocarcinoma cell line

Antibodies were raised in rabbits to purified human term placental villous plasma membrane. These were cytotoxic to human peripheral blood lymphocytes and manifested cross-reactivity to kidney and liver. After absorption with these tissues, reactivity was retained with placental villous plasma membrane. The placental-specific antiserum was fully reactive with BeWo choriocarcinoma cells, but was devoid of reaction with a human myeloma tumor cell line (GM2132). The antibodies were cytotoxic to BeWo in the presence of complement, as determined by trypan blue uptake, 51Cr release, and inhibition of uptake of 3H-thymidine.

Cellular enzyme-linked immunospecific assay (CELISA). IV. Inhibition of endogenous cellular alkaline phosphatase activity

The cellular enzyme-linked immunospecific assay (CELISA) uses ligands conjugated to calf intestinal alkaline phosphatase to quantitate antibody bound to antigens on the surfaces of whole cells. Since the endogenous alkaline phosphatase present in many cell types contributes unwanted background noise to the assay, ways of inhibiting endogenous cellular alkaline phosphatase were investigated. We found that the endogenous alkaline phosphatase in human peripheral blood mononuclear cells was incompletely inhibited by EDTA or L-cysteine. Levamisole, however, inhibited endogenous cellular alkaline phosphatase completely without impairing the sensitivity of the CELISA. The use of levamisole is recommended for assays that use alkaline phosphatase conjugates to detect molecules on the surfaces of cells that also contain endogenous alkaline phosphatase.

An automatic fluorescence micro-ELISA system for quantitative screening of hybridoma supernatants using a protein-A-beta-galactosidase conjugate

We report on a rapid micro-ELISA screening procedure for the detection of monoclonal antibodies directed against cell surface determinants on lymphoid cells of the mouse. This method employs Terasaki-type trays coated with a monolayer of target cells fixed with 0.02% glutaraldehyde. Cells are incubated with monoclonal antibodies, followed by affinity column-purified rabbit-anti-rat immunoglobulin antibodies and a protein-A-beta-galactosidase conjugate. Binding of antibodies to the cells is visualized by incubation with the substrate 4-methylumbelliferyl galactoside. Fluorescence in the individual wells of the Terasaki trays is then quantitatively analysed within 120 s using a scanning inverted microfluorometer, connected to a digital voltmeter and a desk-top calculator.