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Biomedical subjects

Z Eshhar

Publications and source records attributed to Z Eshhar.

At least 109 records · Page 6Linked to original sources
PubMed1981

Use of monoclonal antibodies to pregnanediol-3 alpha-glucuronide for the development of a solid phase chemiluminescence immunoassay.

Monoclonal antibodies to pregnanediol-3 alpha-glucuronide were produced by hybridomas between P3-X63-Ag8 variants and spleen cell of mice immunized with a bovine serum albumin conjugate of the homologous hapten. The ascites fluid collected from mice inoculated with the cloned hybridoma cells contained antibodies with high specificity and affinity to pregnanediol-3 alpha-glucuronide. A sensitive solid-phase chemiluminescence immunoassay for urinary pregnanediol-3 alpha-glucuronide was established utilizing these antibodies. The assay was validated in terms of specificity, accuracy, sensitivity and precision. When urine samples were assayed for pregnanediol-3 alpha-glucuronide, the results obtained by the solid-phase chemiluminescence immunoassay method and the conventional gas liquid chromatographic method agreed well (n = 30, r = 0.96). The method may be of value for monitoring luteal function since it is fast, sensitive and does not require the use of radioisotopes or purification of the biological sample. Monoclonal antibody preparations facilitate rigorous standardization of the assay.

Animals↗
PubMed1981

Monoclonal antibodies against receptor for epidermal growth factor induce early and delayed effects of epidermal growth factor.

Mice were immunized with human epidermoid carcinoma cells (A-431 cell line) that possess an unusually high number of membrane receptors for epidermal growth factor (EGF). Spleen cells from these mice were fused with NSI cells, a nonsecreting murine myeloma. The immunoglobulins secreted by the obtained hybridomas were screened for specific binding to A-431 cells and selected according to their ability to inhibit the binding of radiolabeled EGF to the membrane of A-431 cells. Several antibodies secreted by cloned hybrid lines were found to inhibit the binding of radiolabeled EGF to membrane receptors of living A-431 cells, human foreskin fibroblasts, and mouse 3T3 fibroblasts and also to membrane preparations from A-431 cells. These monoclonal antibodies induced the early and delayed biological effects mediated by EGF. Like EGF, the antibodies induced morphological changes in A-431 cells and enhanced the phosphorylation of endogenous membrane proteins in membranes from these cells. They also stimulated DNA synthesis in human foreskin fibroblasts. These observations support the notion that the biological information of the EGF-receptor complex resides in the membrane receptor. Furthermore, the antibodies offer a powerful tool to study the structure, processing, and mode of action of EGF receptors.

Animals↗
PubMed1981

Cytotoxic T lymphocyte hybridomas that mediate specific tumor-cell lysis in vitro.

Cytotoxic hybridomas were generated by polyethylene glycol-induced fusion of cytotoxic T lymphocytes (CTL) and BW5147 lymphoma cells. The CTL populations used for fusion were obtained from BALB/c (H-2d) mice primed with leukemia EL4 of C57BL/6 (H-2b) and restimulated either in vivo or in vitro. To circumvent possible CTL-mediated nonspecific lysis of BW5147 cells during fusion, the CTL were transiently inactivated by trypsin prior to fusion. Four cytolytically active hybridomas were obtained, cloned, and subcloned. Hybrid clones lysed all H-2b leukemic target cells tested but not lipopolysaccharide- or concavanalin A-stimulated C57BL/6 lymphoblasts or non-H2b target tumor cells. The mechanism of hybridoma-mediated killing of target cells in vitro appears to be similar to that of parental CTL, although some differences have been observed. The hybridomas appear to possess neither natural killing nor antibody-dependent cytolytic activity. Clones of hybrids propagated in culture for over 6 months without the addition of known external stimulus (i.e., independent of cell growth factor and antigen) exhibit specific lytic activity against H-2b tumor cells. Such autonomous hybridomas will provide a tool for studying the mechanism of CTL-mediated lysis and the nature of the CTL receptors.

Animals↗
PubMed1981

Metastatic properties conferred on nonmetastatic tumors by hybridization of spleen B-lymphocytes with plasmacytoma cells.

The P3-NSI/1-Ag4-1 (NSI) plasmacytoma, when transplanted sc in syngeneic BALB/c mice, grows locally without forming spontaneous metastases. We tested whether somatic hybridization of the NSI cells with spleen B-lymphocytes would render them metastatic in (C57BL/6 X BALB/c) F1 mice. We found that the hybridomas thus produced generated spontaneous metastases with distinct organ specificities. Some hybridomas produced metastases in both liver and spleen, whereas others produced metastases in only the liver. Cells derived from spleen-and liver-seeking hybridomas, when transplanted sc, produced tumors that metastasized to both the liver and spleen. Tumor cells derived from spleen metastasis produced, on transplantation, a tumor that generated spleen metastasis of a larger mass than did tumors derived from liver metastases. Cells derived from liver-seeking hybridomas metastasized to only the liver. Similar patterns of organ specificity were observed after iv injection of the hybridoma cells. The spleen seemed to play determining role in controlling the production of liver metastases by hybridomas that produced both liver and spleen metastases. Such hybridomas did not produce liver metastases when injected into splenectomized recipients. Hybridomas that were only liver-seeking did produce metastases in splenectomized recipients.

Animals↗
PubMed1980

T-cell hybridoma bearing heavy chain variable region determinants producing (T,G)-A--L-specific helper factor.

Thymus-derived lymphocytes (T cells) exert their regulatory effect (help or suppression) on the antibody production by B cells either by direct cell to cell interaction or by soluble mediators or factors. The low frequency of specific T cells, the heterogeneity of their responses and their relatively short life span have hampered the molecular characterization of the antigen recognition unit of T cells, and its structure is largely unknown. The lymphocyte hybridization technique, which has been found very useful for the production of B-cell hybridomas secreting specific monoclonal antibodies, has also been used for the generation of homogeneous and stable T-cell hybridomas with unlimited growth potential. So far the only specific effector function demonstrated in the established T hybridomas is the property to generate a factor(s) which suppresses antibody responses. We now describe the establishment of hybrid lines which exhibit characteristic T-cell markers. One of the hybridomas (denoted R-9) releases into the culture supernatant factor(s) with helper activity specific to the synthetic polypeptide (T,G)-A--L and bears surface determinants of the immunoglobulin heavy chain variable region (VH). Such hybrid cell lines are of great value for studies on the nature of the T-cell receptor.

Animals↗
PubMed1980

Genetic regulation of delayed-type hypersensitivity responses to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys). II. Evidence for a T-T-cell collaboration in delayed-type hypersensitivity responses and for a T-cell defect at the efferent phase in nonresponder H-2k mice.

The intercellular interactions and the site of the genetic defect in delayed-type hypersensitivity (DTH) response to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys) [(T,G)-A--L] has been studied in a system where the T-cell education phase was separated from the efferent phase. In the cellular response, T-T-cell collaboration is required, because T cell-depleted mice were unable to manifest DTH responses after they were transferred with educated and irradiated T cells. Reconstitution of adult thymectomized mice that were irradiated and supplemented with bone marrow cells after treatment with anti-Thy-1.2 serum and complement, with T cells but not with accessory cells gave rise to significant responses. Educated, radioresistant cells required the presence of normal radiosensitive T cells for successful DTH responses to (T,G)-A--L. The genetic defect of nonresponder H-2k and H-2a mice has been located in the above-mentioned, second T-cell population that participates in the efferent phase of this immune reaction. Further characterization revealed that the educated cells are of the Lyt1+ phenotype and that the second normal T cells are expressing the Lyt 1+,2+,3+ phenotype. Thus, the genetic defect of H-2k and H-2a mice in the DTH response to (T,G)-A--L is expressed on the non-antigen-stimulated Lyt 1+,2+,3+ T cells.

Animals↗
PubMed1980

Genetic regulation of delayed-type hypersensitivity responses to poly(LTyr,LGu)-poly(DLAla)--poly(LLys). I. Expression of the genetic defect at two phases of the immune process.

Delayed-type hypersensitivity (DTH) responses served in this study as an experimental model for the analysis of genetic regulations of T-cell responses. Educated irradiated cells from H-2b mice mediated responses in syngeneic recipients, whereas mice of the a, d, f, k, and s haplotypes were nonresponders to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L]. These results suggest that cell-mediated immune responsiveness to (T,G)-A--L is linked to the H-2 complex, as was shown for humoral responses. Educated irradiated T cells of F1 hybrids between high and low responders mediated DTH responses, which indicates that the gene(s) controlling the DTH responses is dominant. To analyze the genetic defect in DTH responses to (T,G)-A--L, we separated the T-cell activation phase from the effector phase that was determined in recipient mice. Two types of nonresponders were observed: (a) When lymphocytes of the a or k haplotypes were educated in a syngeneic environment and then transferred into hybrids between the parental (nonresponder x responder) F1 recipients, DTH responses could have been manifested. (b) On the other hand, no DTH responses could be mediated by transferring educated cells of the H-2s or H-2f origin into the appropriate F1 recipients. In addition, irradiated F1 cells that had been activated to (T,G)-A--L could not mediate DTH responses in both types of nonresponder recipients. These results suggest that T cells of H-2k or H-2a mice can be activated to generate DTH responses to (T,G)-A--L and that the defect in these mouse strains is expressed in another cell population needed for the manifestation of the DTH reaction in the recipient mice. In contrast, T cells of H-2s and H-2f origin cannot be activated to (T,G)-A--L and, thus, fail to manifest DTH responses.

Animals↗
PubMed1980

Immune regulation of experimental myasthenia.

Experimental autoimmune myasthenia gravis (EAMG) is an appropriate model for studying the molecular origin, immunological mechanism and regulation of myasthenia gravis. Several approaches are being utilised for the regulation of the immune response to AChR and for immunosuppression of EAMG: Corticosteriods and azathioprine can suppress EAMG concomitantly with suppression of immune responses to AChR. High dose cyclophosphamide treatment in mice facilitates the onset of EAMG and results in a selective suppression of the humoral response to AChR whereas the cellular response is enhanced. Specific immunosuppression of EAMG is achieved by using a nonmyasthenic, denatured AChR preparation which cross reacts with the intact receptor. Various degradations and modifications of AChR are being performed in order to identify the smallest molecular entity responsible for the myasthenic activity of AChR. Studies on specific monoclonal antibodies, anti-idiotypes, and on the effect of measles virus on EAMG are being described and their possible significance in regulating myasthenia are being discussed.

Acetylcholine↗
PubMed1980

Generation of hybridomas secreting murine reaginic antibodies of anti-DNP specificity.

High frequency of hybridoma lines secreting large amounts of reaginic anti-DNP antibodies were generated by the fusion of splenic lymphocytes enriched by adoptive transfer of immune cells and the NSI plasmacytoma cell line. The murine IgE molecule binds DNP with high affinity and was specifically purified by immunoabsorption. The 190,000 dalton molecule is composed of a lambda-light chain and an epsilon-heavy chain of an apparent m.w. of about 90,000. Absorption studies with anti-class-specific antisera suggest that some of the hybrid clones secrete also a mixed molecule consisting of lambda- and kappa-light chains in addition to the epsilon-heavy chain. The monoclonal reaginic antibody binds to mast cells or rat basophilic leukemia cells and, upon binding of DNP-protein, triggers an anaphylactic reaction.

Animals↗
PubMed1980

Production of hybridomas secreting monoclonal antibodies against components of normal and malignant cells.

The advantages of the lymphocyte hybridization approach has been demonstrated in two systems where monoclonal antibodies of defined specificity have been produced against complex antigens as the acetylcholine receptor and murine carcinoma cells. In both cases it was possible to obtain monoclonal antibodies with specificities that could not be detected in "conventional" antisera. Rare determinants of the AChR were described, one of which is associated with the binding site of cholinergic drugs. A new antigenic marker common to the 3LL metastatic carcinoma and to the lung tissue was defined. A system is described which increases the frequency of positive hybridomas resulted from the utilization for fusion of antibody forming cells that were enriched by antigenic challenge in adoptive transfer system.

Acetylcholine↗
PubMed1979

Induction of secretion of IgM from cells of the B cell line 38c-13 by somatic cell hybridization.

Cells of the murine B cell line 38C-13 possess immunoglobulins of the IgM class on their surface but do not secrete them. Upon hybridization of 38C-13 cells with murine myeloma cells, hybridoma clones were obtained that secreted both pentameric IgM of 38C-13 origin and the myeloma protein. All hybridoma clones synthesized and secreted large amounts of homogeneous IgM with a half disappearance time of about 2 hr, typical of mature plasma cells. Concomitantly with the induction of IgM secretion, the hybridoma cells lost their surface IgM. The possibility of separate pathways for the synthesis of membrane and secreted IgM is discussed.

Animals↗