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J Calafat

Publications and source records attributed to J Calafat.

At least 91 records · Page 5Linked to original sources
PubMed1984

Monoclonal antibodies against human milk-fat globule membranes detecting differentiation antigens of the mammary gland and its tumors.

Mouse monoclonal antibodies have been raised against human milk-fat globule membranes (HMFGM) to obtain reagents for mammary tumor diagnosis. A panel of 17 anti-HMFGM antibodies was selected for further investigation. Antibody-blocking studies indicated that with these antibodies at least nine different non-overlapping epitopes could be distinguished on six different molecules, MAM-1 to MAM-6. Electron microscopic studies of the cellular localization of the antigens detected by some of these antibodies revealed that they were present on the cell membrane mainly, on the microvilli, lining intercellular and intracytoplasmic lumina. The reactivity of the antibodies was studied on normal and tumor tissues and on in vitro cell lines. All antibodies reacted with the resting mammary gland while eight antibodies also bound to breast tumors. None of the antibodies was specific for the mammary gland or its tumors only, but most antibodies also reacted with other epithelial cells, especially of secretory tissues. When tested on a variety of cell lines a distribution reflecting the tissue distribution could be demonstrated. One of the antibodies reacted with nearly all carcinomas and their metastases and did not react with lymphomas, sarcomas, neuroblastomas, melanomas or nervous system tumors. The specificity of the antibodies, tested individually, was not sufficient for further differential diagnosis of the carcinomas, but when some of these antibodies were used in a panel they contribute to an important improvement of the diagnosis.

Antibodies, Monoclonal↗
PubMed1984

Binding of lectins to human mammary tumors: ultrastructural study.

The site of several lectin receptors in human mammary tumors and stroma was studied with the electron microscope. The advantage of the ultrastructural over light microscopic study was that lectin receptors could be localized with precision on the different cell types of the tumor and stroma. Eighteen human mammary carcinomas were incubated with three peroxidase-labeled lectins: peanut agglutinin (PNA), Helix pomatia, and Ulex europaeus I (UEA). These lectins reacted in a selective way; some tumors were negative and others showed reaction in some areas of the tumor and/or the stroma. No correlation was found, however, between the presence of these lectin receptors on the tumor cells and either hormone receptors or histological type of the tumors. These results show that the value of the presence of lectin receptors in human mammary tumors as markers for evaluation of mammary lesions is more complex than thought up to now. The most relevant observations on the stroma cells and inflammatory infiltrates were: (A) Some lymphocytes were positive with PNA, probably representing sessile T cells. In two carcinomas, abundant plasma cells were present in the infiltrates, always with PNA receptors. (B) In all mammary tumors where blood vessels were present in the sections, these were always stained with UEA. This supports the use of UEA as a marker for human endothelial cells even in pathologically altered tissues.

Breast Neoplasms↗
PubMed1983

Specific selection of host cell glycoproteins during assembly of murine leukaemia virus and vesicular stomatitis virus: presence of Thy-1 glycoprotein and absence of H-2, Pgp-1 and T-200 glycoproteins on the envelopes of these virus particles.

Using the indirect immunoelectron microscopy technique, it was investigated whether during assembly of murine leukaemia virus (MuLV) and vesicular stomatitis virus (VSV), the glycoproteins (gp) Thy-1, H-2, Pgp-1 and T-200 present on the surface of BW5147 and BuEL4 leukaemia cell lines were incorporated into the virus envelopes. This work was done mainly with monoclonal antibodies against these gps to exclude the presence of antibodies against endogenous MuLV present in conventional mouse antisera. Thy-1 gps were incorporated into MuLV and VSV envelopes. In contrast, H-2, Pgp-1 and T-200 gps were excluded from the budding of both virus particles. To study whether the presence of Thy-1 gps on the viral envelopes is due to some lateral affinity of this molecule with viral gps, the physical association of Thy-1.1 antigens and MuLV antigens was studied with antibody-induced redistribution of both antigens on the BW5147 cell surface. Antibody-induced patching of the viral antigens did not result in co-patching of the Thy-1.1 antigens. In the reciprocal tests no co-redistribution of viral antigens with Thy-1.1 antigens was seen. These studies show that the presence of Thy-1.1 gp on the MuLV envelope cannot be due to a lateral affinity of this molecule with viral gps and that a selection of surface gps takes place during assembly of MuLV and VSV.

Animals↗
PubMed1981

Independence of H-2 and viral antigens on the cell surface and absence of H-2 antigens on murine leukemia virus and mouse mammary tumor virus particles.

By indirect immunoelectron microscopy we tested for the presence of H-2 antigens on murine mammary tumor virus (MMTV) and murine leukemia virus (MuLV) particles. The association of H-2 antigens and viral antigens on the virus-infected cell surface was investigated with antibody-induced redistribution. Mammary tumor cells and leukemia cell lines with different H-2 genotypes and carrying different MuMTV or MuLV were used. No H-2 antigens could be demonstrated on the envelope of MMTV and MuLV particles, even after the permeabilization of their envelopes with saponin. On the surface of virus-infected cells antibody-induced patching or capping of the viral antigens did not result in copatching or cocapping of the H-2 antigens. In the reciprocal tests no co-redistribution of viral antigens with H-2 antigens was seen. Our experiments failed to show any physical association between H-2 antigens and MMTV or MuLV antigens on the cell surface.

Animals↗
PubMed1981

Morphological study of virus-like particles in two transplantable tumours from BDX rats.

Virus-like particles were found in two transplantable tumours, Sp56 and Sp6, from BDX rats. Sp56, a neurogenic sarcoma, contains abundant C-type particles in all stadia nof morphogeneis. This tumour reacts with anti-Friend leukaemia virus gp70 and anti-Rauscher leukaemia virus p30 sera. Sp6, a fibrosarcoma, has abundant virus-like particles in the cytoplasm, very often associated with centrioles or basal bodies of a cilium. These particles consist of two concentric shells with a diam. of 60 to 65 nm. Released particles were found outside the cell with a diam. of 85 to 100 nm characterized by an envelope and an eccentrically located electron-dense nucleoid, surrounded by an intermediate layer. These virus-like particles show no cross-reaction with antisera against murine C- or B-type particles, but show ultrastructural similarity with virus particles recently described in Chinese hamster cells and in mouse cell lines infected with two retrovirus isolates from South-East Asian mice.

Animals↗
PubMed1981

Molecular heterogeneity of H-2 antigens.

Since the discovery of the H-2Ld molecule (Lemonnier et al. 1975) we have demonstrated that several K and D region alleles produce more than one type of H-2 molecules. Two of four different molecules were distinguished in the products of different alleles. Some of these molecules are products of different genes (H-2D, H-2L), in other instances the evidence for distinct genes is not available. Some of the different molecules produced by the same region might be modified products of the same gene. In the instances where no information implicating different genes is available, we use a neutral terminology which does not presume a genetic difference: H-2K1d and H-2K2d, H-2D1k, H-2D2k, H-2D1dx, H-2D2dx, H-2L1d, H-2L2d, etc. Immunoprecipitation experiments with some anti-H-2L and anti-Qa-2 sera revealed proteins with the apparent molecular weight of 41,000. We designate these antigens provisionally Lq and Qx, respectively. The Lq protein is polymorphic and it is at least partly under the control of H-2L-linked genes since it is absent from BALB/c-H-2dm2 cells. Since we have never seen the 41,000 proteins in precipitates of H-2K or H-2D antigens, it appears that whatever the origin of these molecules, they reveal some features common to products of L and Qa region. The basic relationship of H-2 K, D, L antigens is revealed also by the shared antigenic specificities between these H-2 molecules which we demonstrate using anti-H-2.28 sera. In summary, our results show that the class I antigens in each haplotype represent a family of several distinct but antigenically related molecules. The specificities of the H-2.28 family are the strongest allotype common to different H-2 K, D, and L molecules. Recent direct demonstration of several different genes in the Dd region (Steinmetz et al. 1981) provides evidence for the genetic complexity of H-2 genes which may be underlying basis of the molecular heterogeneity of H-2 antigens discussed here.

Animals↗
PubMed1979

Studies on antibodies against feline leukaemia virus (FeLV) in cat sera and rabbit anti-FeLV sera: cross reaction and differences.

The indirect immunoferritin technique (IFT) that enables us to distinguish clearly whether an antibody reacts with a virus particle or only with the cell membrane, was used to study 25 cat sera and one rabbit anti-feline leukaemia virus (FeLV) serum using FL-74 cells as target. (1) All sera contained antibodies against FeLV even though 11 of the cats were viraemic at the same time; (2) from the effect of glutaraldehyde fixation of the FL-74 cells on the reaction with cat sera and the results of blocking experiments, it could be concluded that cat sera and rabbit anti-FeLV sera react partly with different antigenic specificities of FeLV, partly with the same antigens; and (3) the indirect membrane immunofluorescence test using FL-74 cells as target is not a good test to detect the presence of antibodies against feline oncornavirus-associated cell membrane antigen (FOCMA) because FL-74 cells produce a large quantity of FeLV and the fluorescence measured could be from antibodies against FeLV.

Animals↗
PubMed1978

Type-C oncovirus isolate from human leukemic bone marrow: further in vitro and in vivo characterization.

Rabbit corneal cells transformed by a putative human type-C helper virus pseudotype of the mouse sarcoma virus produce large amounts of transforming and non-transforming viruses. The virions are antigenically related to the woolly monkey (simian) sarcoma-leukemia type-C oncovirus. Typical sarcoma virus lesions developed in newborn rats injected with virus-producing rabbit cells. Cells producing only the putative type-C helper viruses as a result of exposure to a high dilution of transforming virus stock induce lymphosarcomas after inoculation into newborn rats.

Animals↗
PubMed1978

Ultrastructural study of virus-like particles in Chinese hamster lung cells.

Virus-like particles were found in the E36 cells. One type, associated with centrioles, consisted of two concentric shells with a diam. of 50 to 60 nm. Some of these particles were seen budding through the plasma membrane giving rise to a free immature particle showing two concentric shells and an outer envelope. Concentration of the inner shell into a nucleoid results in a mature particle characterized by a nucleoid, mainly eccentrically located, surrounded by an intermediate layer and wrapped in an envelope. The diameter of the nature and immature particles was 75 to 85 nm. The morphogenesis of this virus-like particle resembles that of the oncoviruses.

Animals↗
PubMed1977

Feline malignant mammary tumors. III. Presence of C-particles and intracisternal A-particles and their relationship with feline leukemia virus antigens and RD-114 virus antigens.

Thirty-six feline mammary tumors were examined by the electron microscope, and by the indirect immunofluorescence (IFA) test with anti-FeLV and anti-RD-114 serum. In 11 (30.6%) tumors intracisternal A-particles (IAP) were found. One of these tumors contained a few particles with an electron-dense nucleoid in the cisternae of the endoplasmic reticulum. In 7 (19.4%) other tumors C-particles were found and in the remaining 18 (50.0%) no particles at all could be detected. In 11 (30.6%) tumors FeLV antigens and in 20 (55.5%) tumors RD-114 virus antigens were present. In 9 (25%) tumors we found a high (greater than 1/64) and in 11 (30.6%) tumors a low (greater than 1/16 less than or equal to 1/64) titer. There was a good correlation between the presence of C-particles and the demonstration of FeLV-antigen but none between IAP and FeLV antigens. No correlation was found between RD-114 virus antigens and any type of particle. Morphologically, the IAP found in feline mammary tumors were indistinguishable from the IAP present in mammary tumors of some inbred mice strains. The IAP in feline mammary tumors possibly represent an endogenous virus, different from RD-114 virus. The role of these viruses in the etiology of feline mammary tumors is discussed.

Animals↗
PubMed1977

Levels of mammary tumor virus in hormone-dependent and -independent mouse mammary tumor cells.

Levels of mammary tumor virus particles (types A and B) and levels of the virus antigen were assayed in hormone-dependent and -independent mammary tumors of GR mice. Various transplant generations of seven separate tumor lines were investigated. The results indicated that the tumors consisted of different cell clones, each of which exhibited a separate progressive expression and subsequent loss of the mammary tumor virus. When the tumors were transplanted, levels of B particles first declined in the hormone-dependent cells, but in later transplant generations, the B particle content of the autonomous cells also dropped. In some tumor lines, this was accompanied by a decrease in viral antigens and/or A particles, but in other lines these concentrations remained high. One tumor line (line V) that remained hormone-dependent throughout nine transplantations was practically devoid of B particles but contained high levels of A particles and mammary tumor antigen.

Animals↗
PubMed1976

Antibody-induced modulation and shedding of mammary tumor virus antigens on the surfaces of GR ascites leukemia cells as compared with normal antigens.

The distribution, antibody-induced redistribution, and shedding of murine mammary tumor virus (MuMTV) antigens and the surfaces of GR mouse ascites leukemia (GRSL) cells were studied by the immunoferritin technique and compared with the same activities of thy 1.2 and H-2.8 antigens. MuMTV antigens were redistributed easily and then largely shed from the cell surface; in contrast, H-2.8 antigen moved easily and probably was partially released from the plasms membrane and Thy 1.2 antigen moved slowly and was some what interiorized. The complement-dependent cytotoxicity test was used to study the possibility of antigenic modulation for these cell-surface antigens from the surface of the GRSL cells could be modulated by preincubation with anti-MuMTV serum, in contrast to H-2.8 and Thy 1.2 antigens. The results obtained with the immunoferritin technique and the cytotoxicity test correlated well and sug-ested that the shedding of MuMTV antigens from the cell surfaces may occur in vivo, providing the tumor a way to escape from the immune defense of the host. Thy 1.2 and H-2.8 antigens were present on the envolope of B and C particles, which suggested that these viruses do not select a Thy 1.2 or H-2.8-negative area of the GRSL cell surface as amaturation site.

Animals↗
PubMed1976

Virus-like particles in bovine sera for tissue culture.

Virus-like particles were found in nine different bovine sera for tissue culture from commercial suppliers. These particles were spherical with an overall diam. between 70 and 95 nm. After negative staining, surface projections of about 11 to 12 nm were clearly seen. One of the nine sera was positive in an Ouchterlony test with antisera against bovine viral diarrhoea virus.

Animals↗
PubMed1975

Immunologic, virologic, and genetic aspects of mammary tumor virus-induced cell-surface antigens: presence of these antigens and the Thy 1.2 antigen on murine mammary gland and tumor cells.

The distribution of the normal differentiation antigen Thy 1 and the mammary tumor virus (MTV)-induced antigens or antigen complexes MLm and MLr were studied in mouse mammary gland cells, mammary tumor cells, and other cell types, by use of ascites leukemia cells of the GR mouse strain as target cells in the cytotoxicity test. The Thy 1.2 antigen was detected by an AKR antiserum to C3Hf thymocytes. MLm was shown by a homologous C57BL antiserum to GRSL2 leukemia (absorbed in vivo in GR mice); MLr was detected by a rabbit heterologous antiserum (absorbed in vivo in C57BL or GR mice and in vitro with BALB/c milk) prepared against Tween 80- and ether-treated purified B particles. Sera from Sprague-Dawley rats bearing murine leukemia virus (MuLV)-producing syngeneic tumors were not cytotoxic or only slightly cytotoxic for GR leukemias transplanted in vivo, which indicated that MuLV-induced antigens were absent or present in very low quantity in such leukemias. The MLr and MLn antigens or antigen complexes were possibly identical to the mammary leukemia (ML) antigen, since they could be detected not only on GR but also on DBA/2 leukemia cells and since their distribution was exactly the same as that of MTV. Both the MLr and MLm antigens were present in purified B particles, and antigenic activity were present in purified B particles, and antigenic activity was enhanced by destruction of the purified virus particles. The antigens were about eightfold enriched in a preparation of B-particle envelopes, as shown by quantitative cytotoxicity absorption (CYTA) tests. Purified nucleoid fractions of B particles were only lightly positive for the antigen, probably due to envelope contamination. One dominant gene was responsible for the expression of MLr, as shown by CYTA tests with mammary glands of individual animals of segregating crosses between the GR strain with high mammary cancer incidence and strains with low incidence. This gene was closely linked with or was possibly identical to 1) the gene for cytoplasmic MTV gs antigen expression as seen by fixed cell immunofluorescence, and 2) the gene causing mammary tumors in the GR mouse strain.

Animals↗