Immunological recognition of the prolactin receptor: identification of a single binding unit of molecular weight approximately 42,000

Different polyclonal and monoclonal antibodies against the rabbit mammary prolactin (PRL) receptor were previously obtained that totally inhibited PRL binding in the rabbit mammary gland. Only polyclonal antibodies were shown to immunoprecipitate preformed PRL--receptor complexes in solubilized mammary membranes suggesting that they also recognized domains outside of the PRL binding site of the receptor. When partially purified PRL receptor preparations from both rabbit and pig mammary tissues were iodinated, immunoprecipitated and subsequently analyzed by SDS--PAGE, a single component of molecular weight approximately 42,000 was specifically recognized by all the anti-PRL receptor antibodies. This unit was the only component immunoprecipitated by the monoclonal antibody M 110. Its identification was not impaired by using reducing or non-reducing conditions. Moreover, a further purification of the [125I]-labeled receptor preparations from both species by a second PRL affinity chromatography selected a single binding unit of the same molecular weight. In contrast, polyclonal antibodies immunoprecipitated additional components apart from the 42,000 unit, especially one unit of molecular weight 70,000-80,000 in both species. We conclude that rabbit and pig mammary PRL receptors exhibit striking immunological similarities. Both contain a single binding unit of molecular weight approximately 42,000 that is not linked to other units via disulfide bridges. This binding unit could be associated with a larger component of MW 70,000-80,000 in the holo receptor.     

Monoclonal antibodies to antigens abnormally expressed in breast cancer

We report the production, screening, and characterization of ten murine monoclonal antibodies directed at antigens that are expressed abnormally in human breast tumors. Immunoperoxidase staining of frozen and fixed tissues shows the antigens to be present at low levels on the luminal membrane of normal breast cells and at high levels in the cytoplasm and surface membrane of breast tumor cells. The ten antibodies appear to recognize six different epitopes on the basis of their quantitative differences in reactivity against four antigen preparations, as measured by ELISA. Immunoblots show that eight of the ten antibodies recognize a 300,000 MW molecule from breast tumor preparations; six of these antibodies also react with a second molecule from the same tumor preparations of 280,000 MW. Seven antibodies react with an antigen from milk fat globule membrane of 330,000 MW. It therefore appears that the two molecules from tumor tissue and the one molecule from normal tissue share common epitopes. Selected antibodies were tested for reactivity against 25 primary breast tumors and 14 pairs of primary and metastatic breast tumors. Three antibodies have broad reactivity and stain more than 80% of primary tumors; the three other antibodies identify subsets of those tumors. Results of staining pairs of primary and metastatic lesions show that metastases continue to express antigens of the primary lesion in a high percentage of cells.     

Expression of monoclonal-antibody-defined antigens in fractions isolated from human breast carcinomas and patients' serum

The aim of this study was to examine tissue from patients with breast carcinoma or benign breast disease for the presence of monoclonal-antibody-defined antigens, including the MUC1 mucin and carcinoembryonic antigen CEA. The tests were performed by sodium dodecyl sulphate/polyacrylamide gel electrophoretic separation of proteins, electrophoretic transfer to nitrocellulose membranes and immunostaining with the monoclonal antibodies. Some of the antigens identified are known to circulate at high levels in some but not necessarily all, breast carcinoma patients. Serum from a panel of ten breast cancer patients was subjected to a fractionation procedure designed to release antigen from immune complexes, and again these smaples were analysed for the presence of monoclonal-antibody-defined antigens. A high frequency of positive reactions was detected by the anti-MUC1 monoclonal antibody C595 with both breast carcinoma subcellular membrane fractions as well as antigen fractions eluted from circulating immune complexes. No reactions were observed with equivalent materials from benign breast disease samples. The findings illustrate the variability in antigen expression between breast tumours. The data also indicate that a proportion of patients respond to their tumour by the production of antibodies that recognise the MUC1 antigen in their circulation.     

Identification of three antigens in human brain associated with similar antigens on human leukaemic cells.

Monoclonal antibodies prepared against a non-T and non-B acute-lymphocytic-leukaemia cell line were tested for reactivity against human brain tissue. Several of the monoclonal antibodies were found to react specifically with brain fractions. Three antigens, 44H4, 44D7 and 44D10, were identified in white matter. Although 44D10 was absent from grey matter, the levels of 44H4 and 44D7 antigens present in grey matter were 2- and 4-fold higher respectively than in white matter. Fractionation of white matter indicated that all three antigens were absent from the multilamellar compact myelin, but associated with a membrane fraction of higher density. All three antigens, which required detergent for solubilization from the membranes, were purified by affinity to monoclonal antibodies and/or were analysed by immunoblotting. The 44H4 and 44D10 antigens were single polypeptide chains with Mr 94000 and 80000 respectively when resolved by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Monoclonal antibody 44D7 reacted with a complex of a Mr greater than 120000 under non-reducing conditions in the presence of sodium dodecyl sulphate. This complex dissociated on reduction into four bands with Mr values of 80000, 57000, 47000 and 41000. The brain antigens are present on proteins similar to, or identical with, those isolated from acute-lymphocytic-leukaemia cells.     

MUC1 and cancer

The MUC1 membrane mucin was first identified as the molecule recognised by mouse monoclonal antibodies directed to epithelial cells, and the cancers which develop from them. Cloning the gene showed that the extracellular domain is made up of highly conserved repeats of 20 amino acids, the actual number varying between 25 and 100 depending on the allele. Each tandem repeat contains five potential glycosylation sites, and between doublets of threonines and serines lies an immunodominant region which contains the epitopes recognised by most of the mouse monoclonal antibodies. The O-glycans added to the mucin produced by the normal breast are core 2 based and can be complex, while the O-glycans added to the breast cancer mucin are mainly core 1 based. This means that some core protein epitopes in the tandem repeat which are masked in the normal mucin are exposed in the cancer associated mucin. Since novel carbohydrate epitopes are also carried on the breast cancer mucin, the molecule is antigenically distinct from the normal breast mucin. (Changes in glycosylation in other epithelial cancers have been observed but are not so well documented.) Immune responses to MUC1 have been seen in breast and ovarian cancer patients and clinical studies have been initiated to evaluate the use of antibodies to MUC1 and of immunogens based on MUC1 for immunotherapy of these patients. The role of the carbohydrates in the immune response and in other interactions with the effector cells of the immune system is of particular interest and is discussed.     

Accessibility of antigenic sites recognized by AUA1, HMFG1 and HMFG2 monoclonal antibodies: its influence on antibody binding of live cells

We assessed the immunoreactivity of live and alcohol-fixed monolayers of HRA-19, a rectal adenocarcinoma cell line, to the monoclonal antibodies AUA1, HMFG1 and HMFG2. Differences in staining patterns between live and alcohol-fixed colonies were found. The well-polarized cells forming the centers of the monolayer colonies showed strong membrane staining when the cells were alcohol-fixed prior to AUA1 incubation, but showed no staining when the cells were alive during the incubation. When AUA1 incubation was done both before and after alcohol fixation, membrane staining was again seen, ruling out the possibility of antigenic modulation. Incubation of live cells with AUA1 together with EDTA showed strong staining of dissociating cells. It is concluded that AUA1 antigenic sites, which on polarized cells are basolateral in location, are inaccessible to the antibody-containing culture fluid, which bathes the apical aspects of the cells, but they become accessible after alcohol fixation, or treatment with EDTA. HMFG1 antigenic sites are located on the apical cell membrane, and accordingly, no differences were seen between incubation of live and alcohol-fixed cells when incubated with HMFG1. The antigenic sites of HMFG2 are partly intracellular, and in our monolayer model, the staining of live cells was weaker and more scarce than on alcohol-fixed cells. It is concluded that immunostaining of cytological and histological material of tumours may not adequately predict antibody binding on live cells, and thus, these findings are of importance in the context of selection of monoclonal antibodies for clinical radio-immunotargeting.     

Characterization of cell surface antigens of human mammary epithelial cells with monoclonal antibodies prepared against human milk fat globule

Hybridomas have been prepared that secrete monoclonal antibodies against three different surface antigens of normal human mammary epithelial cells by fusion of mouse myeloma cells with spleen cells from mice and rats immunized with delipidated human milk fat globules. Using a novel method for molecular weight determination, the three different monoclonal antibodies, BLMRL-HMFG-Mc3, BLMRL-HMFG-McR2, and BLMRL-HMFG-Mc5, were found to identify molecules with apparent molecular weights of 46,000, 70,000, and 400,000 daltons, respectively. The latter is a mucin-like glycoprotein with a high sugar content and has not previously been described as a component of the human milk fat globule or of human mammary epithelial cell membranes. Single-cell quantitation of binding of monoclonal BLMRL-HMFG-Mc5 to three breast tumor cell lines using a Microscope Spectrum Analyzer and indirect immunofluorescence revealed a heterogeneous expression. Further, using a competitive radioimmunoassay, it was found that breast tumor cell lines differed by at least 10-fold in the 400,000-molecular-weight antigen content. None of the three antigens are detectable on several nonbreast cell lines, including normal breast fibroblasts.     

Differential expression of the glycosylated forms of MUC1 during lung development

Human MUC1 mucin is a high-molecular weight transmembrane glycoprotein expressed on the apical surface of the simple epithelia of many different tissues. Previous investigations suggest the involvement of MUC1 in epithelial cytodifferentiation and glandular morphogenesis. However, the role of MUC1 in the development of the fetal respiratory tracts has so far been poorly investigated. To obtain more information on the roles of MUC1 during fetal lung development, we examined the expression and distribution of MUC1 by immunohistochemical staining of postmortem lung specimens from fetuses and neonates of various gestational ages. Three monoclonal antibodies, HMFG1, HMFG2, and anti-KL-6, which bind different glycosylation variants, were used. Each monoclonal antibody has been shown to recognize heavily-glycosylated MUC1, sparsely-glycosylated MUC1, and sialylated carbohydrate side chains of MUC1, respectively. At 13 weeks of gestation, the terminal respiratory tracts were diffusely stained with HFMG1 and anti-KL-6. Sparsely-glycosylated MUC1, as recognized by HMFG2, was detected only in the distal portions of the terminal bronchioles that divided into respiratory bronchioles. As such development continued, MUC1, recognized by HMFG1 and anti-KL-6, was detected throughout the bronchioles and terminal sacs, although HMFG1 immunoreactivity decreased in intensity towards the terminal sacs. Sparsely-glycosylated MUC1, as recognized by HMFG2, was mainly observed in the terminal portions. In the adult lungs, both the alveolar spaces and the respiratory bronchioles stained with HFMG1 and anti-KL-6. However, the distribution of sparsely-glycosylated MUC1 was limited in the alveolar epithelial cells. Our investigation demonstrated that variants of MUC1 were expressed in the fetal respiratory tracts as early as 13 weeks of gestation, and its expression persisted even after lung maturation. The precise roles of MUC1 were not determined in the present study; however, different glycosylation variants of MUC1 may be associated with the development of different regions of the terminal respiratory tract.     

Chain specificity assignment of monoclonal antibodies to human laminins by using recombinant laminin beta1 and gamma1 chains.

In the present study, the chain specificity of 16 commonly used monoclonal antibodies to human laminin(s) was analysed by using recombinant laminin beta1 and gamma1 chains. By ELISA, all antibodies reacted with purified placenta laminin, and most antibodies recognised either recombinant beta1 or gamma1 chains. Reactivity and chain specificity was confirmed against the recombinant chains in Western blotting under non-reducing conditions, and only a few antibodies were reactive under reducing conditions. Most antibodies were able to immunoprecipitate associated laminin beta1/gamma1 chains from platelet lysates. Based on these results and data from the literature, a tentative epitope map is presented.     

Separation of luminal and abluminal membrane enriched domains from cultured bovine aortic endothelial cells: monoclonal antibodies specific for endothelial cell plasma membranes

Two kinds of membrane (luminal and abluminal membrane domains) fractions have been isolated from bovine aortic endothelial cells by fractionation of whole cell homogenate on discontinuous sucrose density gradients. The luminal membrane domain was enriched 12-16-fold for angiotensin-converting enzyme activity and 8-10-fold in alkaline phosphatase activity. The abluminal membrane domain displayed an enrichment of 8-fold in (Na+ + K+)-ATPase activity. Both of the membrane domains were minimally contaminated with mitochondria, microsomes and Golgi bodies, as assessed by their corresponding marker enzyme activities. 125I-labeling of endothelial cell monolayers by the Enzymo-Bead lactoperoxidase-catalyzed iodination procedure, followed by isolation of membranes, revealed that the radioactivity was predominantly associated with membranes enriched in angiotensin-converting enzyme activity, corresponding to the luminal membrane domain. However, when cells were radioiodinated in suspension culture, radioactivity was found equally associated in both the luminal and abluminal membrane fractions. Electron microscopy of freeze-fractured and sectioned material showed both luminal and abluminal membrane domains to be in the form of vesicles varying in size from 100 to 400 nm in diameter. To characterize the separation of endothelial cell membrane domains, we have attempted to prepare monoclonal antibodies specific for endothelial cells. Several clones were obtained, producing antibodies which bound to endothelial cells of arterial, venous and capillary origin. Two antibodies of these clones, XIVC6 and XVD2, were studied in more detail. In the ELISA assay, these antibodies reacted with bovine vascular endothelial cells, but not with human umbilical cord endothelial cells, nor with bovine corneal endothelial cells, smooth muscle cells or fibroblasts. Both of these antibodies are directed against an antigen of approximately 130 kDa, under reducing and non-reducing conditions, as assayed by the immunoprecipitation method. Western blot analysis of luminal and abluminal membrane fractions revealed that only MAb XVD2 reacted with an antigen, indicating that the antibody XIVC6 is directed against an epitope which is denatured by SDS. Moreover, MAb XVD2 preferentially reacted with the luminal membrane compared to the abluminal membrane domain of the endothelial cell. These monoclonal antibodies do not react with platelet membrane proteins, indicating that this 130 kDa membrane antigen is not common to both endothelial cells and platelets.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characterization of antigens recognized by new monoclonal antibodies raised against culture filtrate proteins of Mycobacterium bovis bacillus Calmette-Guérin

Effective protection against Mycobacterium tuberculosis may be achieved in experimental animals by immunization with proteins secreted by tuberculous bacilli in the extracellular milieu during growth. In this study, monoclonal antibodies were raised against Mycobacterium bovis bacillus Calmette-Guérin (BCG) culture filtrate proteins or live BCG, in an attempt to identify novel mycobacterial secretion antigens: the localization of the antigens recognized by the monoclonal antibodies within the mycobacterial cell was studied and interspecies reactivity was also investigated. The monoclonal antibodies obtained recognized proteins of molecular mass ranging from 5 to 82 kDa, with a prevailing frequency in the 30 kDa region. Three of the monoclonal antibodies recognized proteins present only in culture filtrates, one reacted with a cytoplasmic antigen, while the remaining antibodies recognized components which were mainly associated with the cell wall and the cytoplasmic membrane. The chemical nature and possible identity of the antigens was checked. Three monoclonal antibodies are likely to react with novel mycobacterial antigens of 5, 42 and 82 kDa, respectively.     

Shared idiotypes of human peripheral blood B and T lymphocytes.

In a patient with an IgG lambda monoclonal serum component possessing anti-streptolysin O activity, we have demonstrated peripheral blood B and T lymphocytes with shared or similar idiotypes. The idiotypic T lymphocyte membrane structure was capable of binding the specific antigen (SLO). After radioiodination and subsequent detergent solubilization of the same T cell population, immunoprecipitation of the lysate by employing anti-idiotypic antibodies, resulted in the isolation of a polypeptide chain with a m.w. of 70,000 on SDS polyacrylamide gels under reducing conditions. The polypeptide expressed no isotypic immunoglobulin markers. Internal labeling experiments indicated that this membrane structure was actively synthesized by the T lymphocytes.     

Synthesis and antibody recognition of mucin 1 (MUC1)-alpha-conotoxin chimera.

We synthesized and characterized new chimera peptides by inserting an epitope of the mucin 1 glycoprotein (MUC1) as a 'guest' sequence in the 'host' structure of alpha-conotoxin GI, a 13-residue peptide (ECCNPACGRHYSC) isolated from the venom of Conus geographus. The Pro-Asp-Thr-Arg (PDTR) sequence of MUC1 selected for these studies is highly hydrophilic and adopts a beta-turn conformation. The alpha-conotoxin GI also contains a beta-turn in the 8-12 region, which is stabilized by two disulphide bridges in positions 2-7 and 3-13. Thus, the tetramer sequence of alpha-conotoxin, Arg9-His-Tyr-Ser12, has been replaced by PDTR, comprising the minimal epitope for MUC1 specific monoclonal antibodies (MAbs) HMFG1 (PDTR) and HMFG2 (DTR). Synthesis of the chimera peptide was carried out by Fmoc strategy on (4-(2',4'-dimethoxyphenyl-aminomethyl)phenoxy) (Rink) resin and either 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB) or air oxidation was applied for the formation of the first Cys3-Cys13 or Cys2-Cys7 disulphide bridge, respectively. For the second disulphide bridge, three different oxidation procedures (iodine in acetic acid, 10% DMSO/1 M HCl or tallium trifluoroacetate (Tl(tfa)3) in TFA) were utilized. The HPLC purified peptides were characterized by electrospray mass spectrometry (ES-MS) and amino acid analysis. The CD spectra of the bicyclic MUC1-alpha-[Tyr1]-conotoxin chimera peptide showed partially ordered conformation with turn character. In antibody binding studies, the RIA data showed that both the linear and the bicyclic forms of MUC1-alpha-[Tyr1]-conotoxin chimera were recognized by MAb HMFG1 specific for PDTR sequence, while no binding was observed between MAb HMFG2 and various forms of the chimera. MAb HMFG1, using synthetic epitope conjugates or native MUC1 as target antigens, recognizes the PDTR motif more efficiently in the linear than in the bicyclic compound, but no reactivity was found with the monocyclic forms of MUC1-alpha-[Tyr1]-conotoxin chimera, underlining the importance of certain conformers stabilized by double cyclization.     

The protective activity of polyclonal and monoclonal antibodies to the lipopolysaccharide of Neisseria meningitidis serogroup A in in vivo experiments

The protective activity of the sera of mice immunized with the preparations of native and detoxified N. meningitidis lipopolysaccharide (LPS), group A, as well as with monoclonal antibodies to N. meningitidis antigens, groups A and B, was studied on the mucin model of meningococcal infection. The study showed that the maximum level of anti-LPS antibodies in mice was observed on day 7 after the injection of LPS. Immune sera obtained from mice were capable of protecting the animals from fetal meningococcemia induced by N. meningitidis strains of homologous and heterologous groups. As shown by the results of this study, the alkaline treatment of N. meningitidis native LPS did not decrease the protective properties of antibodies. The monoclonal antibodies under study were found to possess high preventive activity in mice challenged with N. meningitidis, groups A and B. Anti-LPS monoclonal antibodies showed greater protective activity than antipolysaccharide monoclonal antibodies.     

Brain-associated glycoproteins expressed in bovine heart purkinje fibres

Summary The Purkinje fibres of bovine heart were investigated immunohistochemically by use of monoclonal antibodies with specificity against the glycoproteins Thy-1 and Gp120, expressed in human brain. The existence and expression in bovine tissues (brain and thymus) of antigens displaying similar properties and immunochemical crossreactivity with monoclonal antibodies against the human antigens were confirmed.Both these antigens, as identified by use of anti Thy-1 and anti-Gp120 monoclonal antibodies were found to be associated with the membranes of the impulse conduction system. The presence of the antigens was seen in areas facing other conduction cells. No parts of the cells facing the basal membrane of the fibres were stained. The continuous staining between the cells was different from that of desmosome related proteins. These findings may have physiological and functional implications and are interesting in relation to recent evidences suggesting that the conduction tissue might be a derivative of the neural crest.     

Brain-associated glycoproteins expressed in bovine heart Purkinje fibres.

The Purkinje fibres of bovine heart were investigated immunohistochemically by use of monoclonal antibodies with specificity against the glycoproteins Thy-1 and Gp120, expressed in human brain. The existence and expression in bovine tissues (brain and thymus) of antigens displaying similar properties and immunochemical crossreactivity with monoclonal antibodies against the human antigens were confirmed. Both these antigens, as identified by use of anti Thy-1 and anti-Gp120 monoclonal antibodies were found to be associated with the membranes of the impulse conduction system. The presence of the antigens was seen in areas facing other conduction cells. No parts of the cells facing the basal membrane of the fibres were stained. The continuous staining between the cells was different from that of desmosome related proteins. These findings may have physiological and functional implications and are interesting in relation to recent evidences suggesting that the conduction tissue might be a derivative of the neural crest.     

Reactivity of anti-human milk fat globule antibodies with synthetic peptides

The nucleotide sequence of partial cDNA clones coding for the core protein of a human polymorphic epithelial mucin has recently been obtained, this mucin consists of a highly conserved 60 bp tandem repeat and the amino acids commonly found are PDTRPAPGSTAPPAHGVTSA. We synthesized three peptides, 1) P1.24 containing the 20 amino acids and four amino acids (PDTR) of the adjoining repeat; 2) P1.15 consisting of the first fifteen (PDTRPAPGSTAPPAH) and P1.09 the second nine amino acids (GVTSAPDTR) of peptide P1.24. The reactivities of the synthetic peptides with mAb known to react with breast cancer (BC1, BC2, BC3, HMFG-1, 3E1.2, and RCC-1) were studied. The synthetic peptide, P1.24, corresponding to the antigenic sequence predicted from the tandem repeat reacted with antibodies BC1, BC2, and BC3 (known to react with human milk mucin and mucin expressed in breast cancer) and the antibody HMFG-1 which was used to select the cDNA clones. In addition, the epitopes recognized by BC1, BC2, and BC3 appear to be in the same region of the molecule represented by their reactions with the nine amino acids in peptide P1.09 (GVTSAPDTR). By contrast, other antibodies such as 3E1.2 which reacts only weakly with components of human milk, and RCC-1 that detects a low Mr component (95 kDa) in breast cancer, had no specific reaction with the synthetic peptides, indicating that their epitopes are distinct from those of BC1, BC2, BC3, and HMFG-1. Inasmuch as the antibodies HMFG-1, BC1, BC2, and BC3 react with the fully processed milk mucin, it is likely that some of the peptide is exposed, even in the fully glycosylated molecule. Identification of the different epitopes could lead to the development of "second generation" mAb with enhanced specificity for breast carcinoma using the appropriate synthetic peptides as immunogens.     

Monoclonal Antibodies Identify a Subset of Dense Granules in Cryptosporidium parvum Zoites and Gamonts

ABSTRACT. Two monoclonal antibodies raised against purified oocysts and excysted sporozoites of Cryptosporidium parvum identified antigens located in the anterior half of sporozoites by indirect immunofluorescence microscopic assay. The monoclonal antibodies also reacted with Triton X-100-insoluble antigens of asexual and sexual stage parasites developing in epithelial cells in vitro and identified a 110 kilodalton antigen on immunoblots of sodium dodecyl sulfate-extracted oocysts. Immunoblotting reactivity was abolished by prior treatment of blotted antigen with periodic acid suggesting that the monoclonal antibodies recognize a carbohydrate or carbohydrate-dependent epitope(s). By immunoelectron microscopy, the antibodies reacted with a family of small, electron-dense granules located predominantly in the central region of merozoites and also with a population of cytoplasmic inclusions in macrogamonts. In addition, the monoclonal antibodies prominently labeled the parasitophorous vacuole membrane of all intracellular stages examined suggesting that the corresponding antigen(s) may be exocytosed from the granules to become associated with Triton X-100-insoluble components of the vacuolar membrane or cytoskeleton.     

Human monoclonal antibodies derived from pleural effusion lymphocytes of a patient with breast carcinoma react with human breast cancer-associated antigens and mouse mammary tumor virus polypeptides

Four human hybridoma cell lines (PEB1-4) were established from a fusion of pleural effusion lymphocytes isolated from a breast cancer patient with metastatic disease, 6 years postmastectomy. The hybridomas secreted IgG-k (3 micrograms/ml/10(6) cells). These monoclonal antibodies (PEB1-4) reacted to different degrees with mouse mammary tumor virus (MMTV) and T47D particles (HuMTV). Immunological cross-reaction was also detected with antigens isolated from body fluids of breast cancer patients (BF-Ag). The binding capacity of the monoclonal antibodies (MAbs) PEB1-4 to the above-mentioned antigens was measured by RIA. The specificity of these antibodies was further demonstrated by radioimmunoprecipitation of MMTV, T47D (HuMTV) and BF-Ag. The binding of PEB1-4 to surface antigens of intact cells grown in culture was measured by RIA. Some of the MAbs were shown to bind more avidly to breast cancer cells than to nonbreast cancer cells or nonmalignant cells. The PEB1-4 human monoclonal antibodies may be found useful in analyzing the virus-breast cancer relationship.     

Purification and characterisation of MHC class I antigen from rat liver with monoclonal antibody

We have described three monoclonal antibodies (HAM1, HAM2, and HAM3) to rat liver cell membrane glycoproteins. Recently also we reported another monoclonal antibody (HAM4) to rat hepato-renal membrane antigen. Using these monoclonal antibodies, it is possible to purify membrane antigens. This paper describes the details of the purification and the nature of the antigen purified with one of the monoclonal antibodies (HAM2) to rat liver cell membrane glycoproteins. Antigen was purified with immunoaffinity column. The amino acid composition was determined and compared with those of mice MHC class I antigen (H-2) and with the rat lymphocyte membrane antigens which were purified with monoclonal antibodies and of which amino acids compositions were determined.