Continuous cultures of fused cells secreting antibody of predefined specificity

Production of monoclonal antibodies: strategy and tactics

A myeloma line has been developed which produces no globulin chains of its own, has a duplication of 8.7 h, fuses effectively with B-lymphoblasts and produces stable hybrids. An enhancing effect of macrophages on hybridoma yields has been observed. Among the fusing agents tested, PEG of mol.wt. 4000 gave the best results, 20 degrees C being the optimum working temperature. The maintenance medium of choice has been found to be Iscove's with 10% FCS. Direct exposure of fusion cultures to a selective medium with hypoxanthine, aminopterine and thymidine reduced the labor involved and increased the yield. A mechanical device for changing the medium has been designed. The replacement of standard trays by microtrays resulted in a higher frequency of surviving hybrids. By using a feeder layer, the spleen cell input can be reduced 50-fold. At such low multiplicities the positive cultures arise predominantly from single hybrids, eliminating the need for subsequent cloning. The hybrids can be labelled and will yield in serum-free medium. Since at least a third of them inherit the fast growth rate of their myeloma parent and keep producing over 2000 antibody molecules per second, readaptation to ascitic growth is also superfluous. A simplified technique of producing monoclonal antibodies is given in detail, together with the experimental evidence prompting modifications of the classical method of Köhler and Milstein (1975, 1976).

Secretion of either of a pair of immunoglobulins, IgM or IgX, in somatic hybrid cells derived by fusion of a B-cell lymphoma cell line carrying both immunoglobulin isotypes

The 1.29 cell line is a nonsecreting B-cell leukemia which bears two different immunoglobulin isotypes on its surface, IgM and IgX. The 1.29 cells were hybridized with nonsecreting myeloma cells giving rise to dozens of immunoglobulin secreting hybridomas. These fall into three groups differing in the class of immunoglobulin they secrete. Cells of the first group secrete pentameric IgM (mu, kappa), those of the second group secrete an unknown immunoglobulin, IgX, which may constitute an allotype of IgA, and those of the third group produce light chains only. The two complete immunoglobulins, IgM and IgX, have the same idiotype, as revealed by serological cross-reactivity of an exhaustively absorbed rabbit anti-idiotype serum. The molecular sizes of the heavy chains of the secreted IgM and IgX are slightly smaller than the mu and delta chains, respectively, which are derived from the surface of normal B cells as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Monoclonal antibodies against trophectoderm-specific markers during mouse blastocyst formation

Two-dimensional gel electrophoresis has allowed the detection of proteins characteristic of inner cell mass and trophectoderm in mouse blastocyst. Certain of the proteins characterizing trophectoderm copurify with intermediate filaments from trophectoderm and a trophoblastoma cell line. A monoclonal antibody prepared against proteins of these intermediate filaments labels a filament network in trophectoderm but not in inner cell mass cells.

Monoclonal antibodies specific for dengue virus type 3

Mouse lymphocyte hybridomas were prepared by polyethylene glycol-mediated fusion of cells from a mouse plasmacytoma line with lymphocytes from a mouse hyperimmunized with dengue virus type 3 (dengue-3). Media from 50 hybrid colonies were screened; 46 of them showed antibody activity against dengue-3-infected cells as determined by an indirect immunofluorescent antibody technique. Dengue monoclonal antibody obtained after cloning one of these colonies demonstrated activity in hemagglutination inhibition and indirect immunofluorescent antibody assays with dengue-3 antigen, but not type 1, 2, and 4 antigens. In addition, this antibody activity could be removed from culture media only by absorption with dengue-3 antigen.

Preparation of monoclonal antibodies to xanthine oxidase and other proteins of bovine milk-fat-globule membrane

Nine hybridomas secreting monoclonal antibody to proteins of bovine milk-fat-globule membrane were isolated. All nine cell lines continued to secrete monoclonal antibody after serial transfer in culture and after passage as solid tumours in Balb/cJ mice. Four of the cell lines secreted monoclonal antibody specific for xanthine oxidase, one of the major proteins of milk-fat-globule membrane.

A monoclonal antibody for large-scale purification of human leukocyte interferon

A clone of hybrid myelomas (NK2), secreting a mouse monoclonal antibody to human leukocyte interferon, has been isolated. The antibody neutralizes the antiviral activity of the interferon and, when covalently attached to a solid support and used as an immunoadsorbent, allows interferon purification of up to 5,000-fold in a single step.

Fab2 fragments from HLA xenoantisera specifically block cytolysis mediated by HLA-AB alloantisera

Fab2 fragments from antisera raised in rabbits with partially purified cellular and serum HLA antigens were tested for their ability to block the cytolytic activity of operationally specific HLA-A,B alloantisera. One Fab2 fragment preparation blocked the cytolytic activity of all the HLA-A,B alloantisera tested; the remaining nine inhibited the lytic activity of alloantisera to certain HLA-A,B allospecificities, suggesting that these xenoantisera contain antibody to certain HLA-A,B allotype determinants or to closely associated structures. In contrast to previous reports in the literature none of the xenoantisera contained significant amounts of antibodies to human beta 2-microglobulin.

Monovalent fragments (Fab) of monoclonal antibodies to a sporozoite surface antigen (Pb44) protect mice against malarial infection

Monoclonal antibodies (IG1, k) directed against a surface component of Plasmodium berghei sporozoites (Pb-44) confer complete protection to mice against a lethal inoculum of parasites. The degree of protection is a function of the number of parasites used in the challenge and of the antibody concentration in serum. Passive transfer of 10 micrograms of antibody per mouse abolished or profoundly diminished the infectivity of 10(3) sporozoites, but much higher amounts of antibody were required for complete protection against challenge with 10(4) parasites. Fab fragments of the monoclonal antibodies were as effective as the intact antibodies in mediating protection as determined by the neutralizing assay. This observation suggests that the antibodies interfere with a parasite function necessary for its infectivity, such as, for example, the ability to penetrate into the target cell or to multiply in the hepatocytes. When sporozoites are incubated with the intact monoclonal antibodies at 37 degrees C, a long filament appears at its posterior end (circumsporzoite precipitation [CSP] reaction). Fab fragments are ineffective at high concentrations. However, if after treatment with Fab, the sporozoites are incubated with rabbit antibodies to mouse k-chains, a strong CSP reaction is observed. We conclude that the CSP reaction can result from the cross-linking of Pb44 and that it has the characteristics of a capping reaction followed by the shedding of the immune complexes.

Monoclonal antibodies identify individual determinants on mouse mammary tumor virus glycoprotein gp52 with group, class, or type specificity

Hybrid cell lines producing monoclonal antibodies against the C3H strain of mouse mammary tumor virus (C3H MMTV) were prepared by the fusion of mouse myeloma cells with the lymphocytes of BALB/c mice that were immunized with C3H MMTV. Approximately 10% of the hybrid cells initially plated after cell fusion produced immunoglobulins that reacted in antibody-binding assays with C3H MMTV; 40 of these cells were cloned, and 6 eventually yielded stable cell lines. High concentrations of monoclonal antibodies (5 to 20 mg/ml) were obtained from serum and ascites fluid of syngeneic mice inoculated with the hybrid cells. All of the monoclonal antibodies were directed against the envelope glycoprotein gp52. Three of the hybrid cell lines produced immunoglobulins of the immunoglobulin M subclass and three produced immunoglobulin G2a. The monoclonal antibodies showed limited charge heterogeneity in light and heavy chains when analyzed by high-resolution, two-dimensional gel electrophoresis. Three serologically distinct specificities were observed when these ascites fluids were tested against different strains of MMTV. The antigenic determinants detected were the following: (i) a type-specific determinant unique to the C3H strain of MMTV; (ii) class-specific determinants shared between C3H and GR MMTVs; and (iii) a group-specific determinant found on C3H, GR, RIII, and the endogenous C3H (C3Hf) MMTVs. Because monoclonal antibodies recognize single antigenic determinants, these results demonstrate for the first time that the three patterns of antigenic reactivity for MMTV are related to individual determinants on the gp52 molecule and also clearly show that one strain of MMTV can be distinguished from other strains.

Monoclonal antibodies against simian virus 40 T antigens: evidence for distinct sublcasses of large T antigen and for similarities among nonviral T antigens

We have isolated three clones of hybrid cells which synthesize antibodies specific for determinants on simian virus 40 (SV40) T antigens. Mouse myeloma NS1 cells were fused with spleen cells from mice that had been immunized with SV40-transformed mouse cells. Hybrid cells were selected in HAT medium and cloned in soft agar. We used an enzyme-linked immunosorbent assay for detection and quantification of mouse antibodies against SV40 T antigens. Monoclonal antibodies from 3 of the 24 clones that scored as positive in the enzyme-linked immunosorbent assay were verified by immunoprecipitation to be specific for SV40 T antigens. Two clones (7 and 412) produced antibodies that recognized denaturation-sensitive antigenic determinants unique to large T antigen. Antibodies from clone 7 appeared to have a low affinity for large T antigen. Antibodies from clone 412 had a higher affinity for large T antigen but did not recognize a subclass of large T antigen that was recognized by tumor serum. Antibodies of the third clone, clone 122, recognized a denaturation-stable antigenic determinant of the 53,000-dalton mouse nonviral T antigen in SV40-transformed cells. Antibodies from clone 122 also recognized similar (51,000- to 56,000-dalton) nonviral T antigens in SV40-transormed or lytically infected cells from five mammalian species and in four uninfected mouse lines. From these observations, we have concluded that (i) the 94,000-dalton SV40 large T antigen may exist as immunologically distinguishable subclasses, and (ii) the nonviral T antigens of five mammalian species share at least one antigenic determinant.

Transformation-related antigens identified by monoclonal antibodies

Tumor-cell proteins that were antigenic in a syngeneic animal were identified by immunoprecipitation with monoclonal antibodies. Spleen cells of BALB/c mice immunized with plasma membranes of Kirsten RNA sarcoma virus-transformed BALB/3T3 cells were fused with NS-1 myeloma cells. Antibodies secreted into the culture fluid from these hybridomas were distinguished by their reactivity against proteins of different target cells. A total of 191 cultures were established; 143 produced antibodies that bound to BALB/3T3 cells transformed by the RNA sarcoma virus, of which antibodies from 82 bound to BALB/3T3 transformed with simian virus 40, and antibodies from 56 bound to BALB/3T3 cells. Thus, more than 50% of the cultures produced antibodies that possibly were specific to antigens of the transformed cell. Twenty different hybridomas have been cloned, and antibodies, from eight of these were found to immunoprecipitate five different proteins. A protein of approximately 32,000 daltons was precipitated from BALB/3T3 cells transformed by the RNA sarcoma virus, simian virus 40, or methylcholanthrene but not from untransformed BALB/3T3 cells. A protein of about 300,000 daltons was precipitated from all four cell lines; precipitation was enhanced in the viral transformed cells. Proteins of approximately 57,000, 54,000, and 8500 daltons were immunoprecipitated from all four cell lines.

Identification of a p69,71 complex expressed on human T cells sharing determinants with B-type chronic lymphatic leukemic cells

In the course of generating monoclonal antibodies to human thymus-dependent differentiation antigens, we were able to define specificities shared by T cells and by cells from patients with chronic lymphatic leukemia that were not detectable on normal B cells. In particular, one of these antibodies was reactive by indirect immunofluorescence with greater than 95% of the thymocytes and 80--95% of nonadherent sheep erythrocyte-rosetting peripheral blood lymphocytes (PBL), but was unreactive with normal B cells or cell lines derived from PBL by Epstein-Barr virus transformation. However, the leukemic cells from 11 of 14 patients with B-type chronic lymphatic leukemia were found to express detectable concentrations of this surface determinant. The target antigen recognized by this monoclonal antibody was shown by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be a p69,71 complex. Our findings suggest a possible relationship between this antigen and the previously described GIX system in the mouse.

Mechanism of effector-cell blockade. I. Antigen-induced suppression of Ig synthesis in a hybridoma cell line, and correlation with cell-associated antigen

A mouse hybridoma cell line, FluIgM-1, which secretes IgM specific for the hapten fluorescein (FLU) was developed to allow detailed analysis of the effector-cell blockade (ECB) phenomenon, in which contact of antibody-forming cells (AFC) with specific antigen results in marked reduction of antibody secretion. Treatment of hybridoma cells with highly substituted FLU conjugates (e.g., Flu20gelatin) resulted in inhibition of plaque formation. The data indicated close parallels with the ECB of normal spleen AFC, both in speed of onset and the dose of antigen required. The inhibition of antibody secretion was confirmed with a biosynthetic-labeling procedure which demonstrated that this was a result of reduced Ig synthesis. The inhibitory effect appeared to be confined to antibody synthesis, in the total protein synthesis, DNA synthesis, and cell-doubling times were unaffected. The association of FLU conjugates with the cells during and following ECB was studied directly using fluorescence microscopy and the fluorescence-activated cell sorter. These experiments showed that FLU conjugates capable of causing blockade aggregated on the cell surface, that the clearance of cell-associated antigen correlated with recovery from ECB, and that at all times when cell associated antigen was detectable, a portion remained bound to the cell surface and was susceptible to enzymatic removal. The latter observations supported previous findings suggesting that ECB was mediated by extracellular antigen. The direct observation of aggregates of antigen on the surface of blockaded cells is consistent with a mechanism involving cross-linking of Ig receptors. Finally, Fc receptors were not present on hybridoma cells, excluding their involvement in induction of ECB.

Formation of hybridoma clones in soft agarose: effect of pH and of medium

Optimal conditions for the formation of hybridoma clones in soft agarose are described. The hybridization frequency is shown to be highly dependent on the pH of the polyethylene glycol (PEG) solution used for fusion and on the cloning medium. Maximal numbers of clones are obtained when the PEG solution used for fusion is at pH 8.0-8.2.

Contribution of dendritic cells to stimulation of the murine syngeneic mixed leukocyte reaction

We have studied the proliferative response of unprimed T cells to syngeneic dendritic cells (DC) (syngeneic mixed leukocyte reaction [SMLR]) in cultures of mouse spleen and lymph node. T cells purified by passage over nylon wool contain few DC and exhibits little proliferative activity during several days of culture. Addition of small numbers of purified syngeneic DC induces substantial, dose-dependent, T cell-proliferative responses that peak at day 4-5. B cells purified on anti-Ig-coated plates do not respond to DC at all doses tested. DC culture medium does not induce proliferation, and coculture of DC and T cells is required. Purified mouse B and T lymphocytes stimulate SMLR weakly if at all. Likewise, peritoneal and spleen macrophages are weak or inactive. Therefore, DC are potent and possibly unique primary cells for stimulating the SMLR in mice. sIg- spleen and lymph node cells show extensive background proliferative responses in vitro, and fail to respond to small numbers of purified DC. If the sIg- cells are treated with anti-Ia and complement, or passed over nylon wool, DC are removed and proliferative activity falls. Proliferative activity is restored by adding back DC at levels similar to those present in sIg- cells (1-2%). Thus, DC-dependent, T cell proliferation probably occurs in all spleen and lymph node cultures. As expected from previous work (6), DC are also potent inducers of allogeneic MLR. On a per DC basis, the syngeneic response is 10 times weaker than the allogeneic MLR, and it is not accompanied by the development of cytotoxic lymphocytes. The magnitude of the SMLR was not altered by antigen priming, and DC maintained in isologous rather than fetal calf serum were active stimulators. Therefore, syngeneic stimulation appears to be an intrinsic property of DC, and modification by exogenous agents does not seem to be required. Coculture of DC and T cells results in the development of cell clusters that can be isolated and characterized directly. The clusters account for 10-20% of the viable cells in the culture, but contain greater than 80% of the responding T cells and stimulating DC by morphologic and surface-marker criteria. The efficient physical association of DC and responding T cells implies specific cell-cell recognition. We conclude that the SMLR reflects the ability of T cells, or some subpopulation of T cells, to interact with and proliferate in response to small numbers of DC.

T-T hybridoma product specifically suppresses tumor immunity

Culture supernatants of spleen or thymus cells from BALB/c mice bearing transplanted, syngeneic, methylcholanthrene-induced sarcomas suppress T lymphocyte-mediated lysis of cells from the tumor borne by the donor of the spleen or thymus cells. On this basis, we hybridized thymus cells from mice bearing sarcoma MCA-1490 with cells from the T lymphoma BW5147. The hybrids (hybridomas) formed were tested for production of factors that could suppress T lymphocyte-mediated lysis of MCA-1490 cells. One hybridoma, and a clone derived from it, produced factors that suppressed the lysis of MCA-1490 cells in vitro. In addition, these factors enhanced the growth of MCA-1490 in immune mice and prevented the destruction of MCA-1490 cells by immune lymphocytes in tumor neutralization (Winn) assays. In vitro lysis of cells from another MCA-induced sarcoma by immune lymphocytes was not suppressed. The suppressor factors did not affect the proliferative response of BALB/c lymphocytes to mitogens or the generation of a cytotoxic response to C57BL/6 alloantigens. Neither did they inhibit the generation of primary or secondary cytotoxic responses to murine leukemia virus-related antigens present on a BALB/c lymphoma line, LSTRA. Although our findings suggest that these suppressor factors are specific for MCA-1490, their specificity for antigens restricted to this tumor needs further definition.

Monoclonal antibody against a 250,000-dalton glycoprotein of Epstein-Barr virus identifies a membrane antigen and a neutralizing antigen

An antibody-secreting hybrid cell line was produced by fusion of mouse myeloma cells with splenocytes from mice immunized with virions of the B95-8 strain of Epstein-Barr Virus (EBV). The monoclonal IgG antibody was shown to have anti-EBV activity by the following criteria: (i) It reacted with the membranes and the cytoplasm of seven different EBV-producing lines, but with no nonproducing line. (ii) The individual cells identified by the murine antibody were shown to be the same cells identified by a human serum having anti-EBV activity. (iii) The antibody significantly reduced the infectivity of two independent strains of EBV (namely, P3HR1K and B95-8). The antigen being recognized was characterized by immunoprecipitations of radiolabeled EBV-producer cell lysates. A single glycoprotein with an estimated molecular weight of 250,000 was identified. It is concluded that neutralization of EBV can be achieved by an IgG-class monoclonal antibody directed against a single antigenic site on a 250,000-dalton glycoprotein, which is a constituent of the EBV virion.

Identification and characterization of rabbit-mouse hybridomas secreting rabbit immunoglobulin chains

Standard cell-fusion techniques have been used to generate hybrid cells from rabbit spleen cells and mouse myeloma cell lines. The hybrids were selected for secretion of rabbit immunoglobulin. Detailed allotype analyses were carried out for 189 cell lines found to be immunoglobulin positive: 1 produced an intact immunoglobulin molecule with antibody activity, 143 produced rabbit light (L) chains, 36 produced rabbit heavy (H) chains, and 9 cell lines gave negative results in tests for group a and b allotypes. Fusions with a nonproducing murine myeloma cell line (SP-2) yielded only L chain-secreting hybrids, whereas 27% of hybrids resulting from fusion with an L chain-producing line (PU) secreted rabbit H chains paired with mouse L chains. Several of the hybridomas have maintained the ability to produce rabbit immunoglobulin chains in culture for almost 1 year and can be propagated as ascites tumors in athymic (nude) mice. Cytogenetic analyses have detected no rabbit chromosomes in the stable hybrid cell lines.

Methods for derivation and detection of anti-parasite monoclonal antibodies

We describe detailed methods for derivation and cloning of myeloma hybrids which secrete antibodies specific for antigens of protozoan parasites. The methods were designed to enable the derivation of large numbers of specific monoclonal antibodies and to give high cloning efficiencies of desired hybrids. Although special attention is paid to derivation and detection of anti-parasite antibodies, the methods can be applied to many different antibody-antigen systems. Using the described methods we have isolated more than 90 myeloma hybrids which secrete antibodies specific for antigens of African trypanosomes and Theileria parasites, thus illustrating their effectiveness.

Quantitation of influenza virus antigens on infected target cells and their recognition by cross-reactive cytotoxic T cells

Monoclonal antibody to type-A influenza virus matrix (M)-protein was used to quantitate the appearance of M-protein on abortively infected P815 cells. After 16 h of infection with different type-A viruses, only a low amount of M-protein appears on the surface of infected cells (approximately 10(3) site/cell) in contrast to approximately 10(5) hemagglutinin molecules on each cell surface. However, virus replication is required for M-protein appearance. Analysis of solubilized membranes purified from 16-h-infected cells shows approximately 10(4) M-protein molecule/cell in the plasma membrane, a content that is consistent with the observed low surface expression, and that indicates that most of the M-protein is localized internally. We found no evidence that cross-reactive cytotoxic T cells could recognize M-protein; neither monoclonal antibody or hyperimmune anti-M-protein antiserum could inhibit T cell killing, either alone or in combination with monoclonal anti-H-2 antibody. Taken together, the low level of M-protein appearance and lack of T cell blocking by anti-M-protein antibody leaves doubt that M-protein is the antigen recognized by cross-reactive cytotoxic T cells.

Monoclonal rat anti-major histocompatibility complex antibodies display specificity for rat, mouse, and human target cells

24 monoclonal rat antibodies are described that are reactive with determinants encoded by the major histocompatibility complex (MHC) of the rat. These hybridoma antibodies were derived by fusing mutant mouse myeloma cells to spleen cells from Lewis rats immunized with allogeneic Brown Norway cells. All 24 antibodies are cytotoxic for both Brown Norway target cells and target cells from the appropriate MHC congenic rats. Pattern of cytotoxicity and hemagglutination strongly suggest reactivity against class I (K or D equivalent) rat MHC determinants. Cytotoxic cross-reactivity patterns were generated for each monoclonal antibody on a panel of rat and mouse lymphoid cells and human peripheral T lymphocytes. A high degree of interspecies cross-reactivity was noted with approximately one-half of the antibodies positive on human and/or mouse target cells. 11 antibodies recognized polymorphic determinants in the mouse, and, by using target cells from MHC congenic mouse strains, it was shown that these determinants are encoded by genes within the H-2 complex. Finally, by considering the overall reactivity patterns of these monclonal antibodies on all target cells, one can show that these 24 antibodies represent a minimum of 14 antibody specificities.

Vertebrate cells express protozoan antigen after hybridization

Epimastigotes, the invertebrate host stage of Trypanosoma cruzi, the protozoan parasite causing Chagas' disease in man, were fused with vertebrate cells by using polyethylene glycol. Hybrid cells were selected on the basis of T. cruzi DNA complementation of biochemical deficiencies in the vertebrate cells. Some clones of the hybrid cells expressed T. cruzi-specific antigen. It might be possible to use selected antigens obtained from the hybrids as vaccines for immunodiagnosis or for elucidation of the pathogenesis of Chagas' disease.

Immunoglobulin chain loss in hybridoma lines

Hybrid cells secreting one, two, or three different immunoglobulins were constructed. The loss of immunoglobulin heavy or light chain expression was monitored. Chain loss was random only in lines with an excess of active light chain genes over heavy chain genes. In all other combinations preferential heavy chain loss was observed. Variant cells altered in heavy or light chain synthesis exhibited an altered chain loss pattern. It is therefore proposed that free immunoglobulin heavy chain is toxic for the cells. The interdependence of the two gene products gives a possible molecular explanation of apparent directed chromosome loss in hybrid cells.

Substance P: a carotid body peptide

Immunofluorescent studies have shown that substance P or substance P-like material is present in the cat carotid body, being located in some of the glomus cells and also in nerve axons. About 20% of the glomus cells were substance P positive. Substance P may be stored in glomus cells containing monoamine(s), but further studies are needed to investigate this aspect and also to determine what role, if any, substance P plays in the process of chemoreception.

Use of monoclonal antibodies in an enzyme immunoassay for rapid identification of group B Streptococcus types II and III

Streptococci belonging to Lancefield group B are frequently recognized as the etiological agents of sepsis and meningitis in young children. Current methods of identifying these organisms have not been universally accepted because of the time and complexity in performing the studies and a lack of reference antisera. We have developed hybrid myeloma (hybridoma) cell lines which secrete large amounts of antibody against types II and III group B streptococci. Antibodies harvested from supernatants react only with the bacterial strain that was used initially to immunize the animals. We have used the hybridoma antibodies in an enzyme immunoassay and have shown it to be a sensitive and reliable technique for typing group B streptococci. The use of hybridoma antibodies in the enzyme immunoassay may permit early detection of group B streptococcal antigen before cultures are visibly positive.

Identification of a cell surface protein, p97, in human melanomas and certain other neoplasms

BALB/c mice were immunized with a human melanoma cell line, SK-MEL 28, and their spleen cells were fused with mouse NS-1 myeloma cells. Hybrid cells were tested in an indirect 125I-labeled protein A assay for production of antibodies that bound to surface antigens of SK-MEL 28 melanoma cells but not to autologous skin fibroblasts. One hybridoma, designated 4.1, had the required specificity. It was cloned and grown in mice as an ascites tumor. The monoclonal IgG1 antibody produced by the hybridoma was purified from the ascites fluid and labeled with 125I. The labeled antibody bound, at significant levels, to approximately 90% of the melanomas tested and to approximately 55% of other tumor cells, but not to three B-lymphoblastoid cell lines or to cultivated fibroblasts from 15 donors. Immunoprecipitation and sodium dodecyl sulfate gel electrophoresis were used to detect the target antigen in 125I-labeled cell membranes of both cultivated cells and tumor biopsy samples. A protein with a molecular weight of 97,000 was identified. This protein, designated p97, was present in both cultured cells and biopsy material from melanomas and certain other tumors, but it was not detected in eight different samples of normal adult epithelial or mesenchymal tissues obtained from five donors.

Artificial carbohydrate antigens: the synthesis of a tetrasaccharide hapten, a Shigella flexneri O-antigen repeating unit

The 8-methoxycarbonyloctyl glycoside of the tetrasaccharide hapten, O-alpha-L-rhamnopyranosyl-(1 leads to 2)-O-alpha-L-rhamnopyranosyl-(1 leads to 3)-O-alpha-L-rhamnopyranosyl-(1 leads to 3)-2-acetamido-2-deoxy-beta-D-glucopyranoside and the trisaccharide glycoside 8-methoxycarbonyloctyl O-alpha-L-rhamnopyranosyl-(1 leads to 3)-O-alpha-L-rhamnopyranosyl-(1 leads to 3)-2-acetamido-2-deoxy-beta-D-glucopyranoside were synthesized by sequential Koenigs-Knorr reactions from monosaccharide units. The tetrasaccharide represents the complete skeletal repeating unit of Shigella flexneri serogroup Y lipopolysaccharide. Both oligosaccharide haptens are functionalized for covalent attachment to proteins, cell surfaces, and solid supports. 1H-N.m.r. evidence for the conformations of these oligosaccharides in solution is presented and shown to be consistent with predictions based on the exo-anomeric effect.

Somatic cell hybrids producing antibodies specific to human fibronectin

We have produced somatic cell hybrids between mouse plasocytoma cells deficient in hypoxanthine phosphoribosyltransferase (P3 x 63 Ag8) and spleen cells derived from mice immunized with purified human plasma fibronectin. We report herein the properties of monoclonal anti-fibronectin antibodies released by eight different clones.

Immunotherapy of colon cancer: prospects for developing immunogenic vaccines based on autologous serological typing

Exploration of specific immunization as a means of cancer therapy has been hampered by the lack of knowledge of human cancer antigens. Recent progress in the serological definition of cell surface antigens of malignant melanomas, renal cancers, and astrocytomas provides a new basis for the construction of immunogenic vaccines and their clinical testing. Application of the same approach to colon cancer depends on the development of methods which permit continuous growth of colon cancer cells in tissue culture.