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D C Benjamin

Publications and source records attributed to D C Benjamin.

At least 55 records · Page 3Linked to original sources
PubMed1984

Monoclonal antibodies to Rous sarcoma virus pp60src react with enzymatically active cellular pp60src of avian and mammalian origin.

The derivation and characterization of 22 hybridoma clones producing monoclonal antibodies (Mabs) specific for the transforming protein of Rous sarcoma virus, pp60src, are described. All Mabs reacted with pp60v-src encoded by Prague, Schmidt-Ruppin, and Bratislava 77 strains of Rous sarcoma virus. Of these Mabs, 10 efficiently immunoprecipitated pp60c-src from chicken embryo cells. Of these 10 Mabs, 2 (GD11 and EB8) readily detected pp60c-src from a variety of rodent and human cultured cells and from rat brain tissue in an in vitro immune complex kinase assay. Mapping experiments have tentatively localized the determinant(s) recognized by GD11 and EB8 to a region of the src protein bounded by amino acid residues 82 to 169, whereas the remaining Mabs appeared to recognize determinants residing within residues 1 to 82 or 169 to 173. Most of the Mabs complexed denatured pp60v-src in a Western immunoblot, and several were used to localize pp60v-src in Rous sarcoma virus-transformed chicken embryo cells by indirect immunofluorescence microscopy.

Animals↗
PubMed1983

Isolation and partial characterization of a monoclonal antibody to the Rous sarcoma virus transforming protein pp60src.

Transformation of cells by Rous sarcoma virus is mediated by the product of the viral src gene, pp60src. A hybridoma cell line producing an immunoglobulin G3 antibody to pp60src was isolated after lymph node cells from immune mice were fused with mouse myeloma cells (P3-NS1-1). Mice were immunized with p60src purified from Escherichia coli cells expressing the src gene product. The monoclonal antibody immunoprecipitated pp60src from Rous sarcoma virus-transformed cells and recognized an antigenic determinant located in the amino-terminal third of the pp60src protein.

Animals↗
PubMed1982

Monoclonal antibodies to the glycoprotein of vesicular stomatitis virus: comparative neutralizing activity.

Nineteen independently isolated hybridomas producing monoclonal antibodies to the glycoprotein of vesicular stomatitis virus were isolated and studied for their capacity to neutralize viral infectivity. By measuring competitive binding of 125I-labeled monoclonal antibodies in a radioimmunoassay. 11 different, non-cross-reacting antigenic determinants were identified on the vesicular stomatitis virus G protein. All monoclonal antibodies reacting with determinants 1, 2, 3, and 4 resulted in viral neutralization, whereas those binding to the other seven determinants did not neutralize infectivity. The mixture of two monoclonal antibodies binding to different determinants resulted in a more rapid neutralization than either antibody alone, suggesting that different antibodies can exert a synergistic effect on viral neutralization. Kinetic experiments revealed biphasic neutralization curves similar to those expected for heterologous antibody. No evidence could be obtained to relate biphasic kinetics of viral neutralization to heterogeneous populations either of antibody molecules or of virus. The possible significance of the kinetic data with monoclonal antibodies is discussed.

Animals↗
PubMed1982

Immune responses to complex protein antigens I. MHC control of immune responses to bovine albumin.

Murine T cell proliferative and antibody responses to the multi-determinant protein bovine serum albumin (BSA) are controlled by Ir genes mapping within the H-2 gene complex. Strains possessing the H-2k, H-2a, and H-2d haplotypes are classified as high responders to BSA. In contrast, H-2b strains are low responders to BSA. Genetic mapping experiments employing strains with recombinant H-2 haplotypes indicate that both T cell proliferative and antibody responses are at least in part regulated by genes within the I-A subregion. Studies on the inhibition of T cell proliferation by monoclonal anti-Ia antibodies are consistent with the assignment of an Ir gene for BSA to the I-A subregion and strongly suggest a role for genes within the I-E/C subregions as well. The MHC-mediated control of antibody responses did not affect the affinity or the isotype of the antibody produced. The relative quantities of antibody specific for each of the three domains of BSA appears to be regulated by H-2-linked BSA Ir genes, and domain III antigenic determinants were found to be dominant in the responses of low-responder mice and in the early response of high-responder mice. This domain III epitope dominance essentially disappears by the tertiary response of high-responder mice.

Animals↗
PubMed1979

Immune response to the src gene product in mice bearing tumors induced by injection of avian sarcoma virus-transformed mouse cells.

A single subcutaneous injection of 10(7) live cells of the highly tumorigenic avian sarcoma virus (Schmidt-Ruppin strain, subgroup D)-transformed BALB/c line into BALB/c mice resulted in the production of an antiserum specific for the avian sarcoma virus gene product pp60src. All sera taken from mice 3 weeks after injection of tumor cells contained antibodies to pp60src. Immunoprecipitation experiments showed that all sera precipitated pp60src from Schmidt-Ruppin-infected chicken cells, but only a portion of these sera precipitated pp60src from chicken cells infected with other strains of avian sarcoma virus, i.e., Prague and Bratislava-77. Analysis of the cross-reactivity patterns of these antisera demonstrated a minimum of three to four antigenic determinants on pp60src. The findings reported here should facilitate the production of monoclonal antibodies to pp60src, which in turn will provide highly specific probes for further investigations into the structure and function of this protein.

Animals↗
PubMed1978

Antibody as an immunological probe for studying the refolding of bovine serum albumin. An immunochemical approach to the identification of possible nucleation sites.

Specifically purified antibody to either domain I, domain III, or to subregions of domains I or III of serum albumin was added to refolding mixtures containing reduced serum albumin but no other refolding catalyst. It was found that the refolding of reduced albumin was greatly enhanced by the presence of specific antibody in the refolding mixture, that this enhancement was restricted to that domain for which the added antibody was directed, and that antibody-mediated enhancement of refolding in the NH2-terminal portion of each domain was delayed as compared to that seen in the COOH-terminal portion of each domain. Thus, an apparent COOH-terminal to NH2-terminal pathway of refolding within each domain was observed, which is consistent with the proposed evolutionary pathway of the albumin molecule and also consistent with the proposed presence of a nucleation center in the COOH-terminal double disulfide loop of each domain.

Antibodies↗
PubMed1978

The antigenic structure of bovine serum albumin. Evidence for multiple, different, domain-specific antigenic determinants.

Using antiserum to native bovine albumin and antigenically active fragments of the protein, we have isolated antibodies directed to each of the three domains and to several subdomains of the albumin molecule. Using albumin and these fragments as inhibitors of the reaction between 125I-albumin and any given antibody population, we have demonstrated that: (a) each domain of albumin is antigenically distinct from each of the other domains; (b) each domain possesses a minimum of two different antigenic determinants; and (c) the entire albumin molecule possesses a minimum of six different, nonrepeating, antigenic determinants.

Antibodies↗
PubMed1978

Tolerance to azobenzenearsonate: preferential loss of the major normal cross-reactive idiotype.

A specific tolerant state was induced in A/J mice to the hapten p-aminobenzenearsonate (Ars) by the injection of deaggregated conjugates of Ars and human gemma-globulin (Ars-DHGG). The kinetics of tolerance to Ars-DHGG was found to be identical to that of B cell tolerance to human gamma-globulin alone. The ability to produce antibody (anti-Ars) bearing the major normal cross-reactive idiotype was found to be preferentially lost. In addition, recovery of the ability to produce anti-Ars bearing this cross-reactive idiotype was found to be delayed as compared to the total anti-Ars response upon spontaneous loss of tolerance.

Animals↗
PubMed1977

Antibody as immunological probe for studying refolding of bovine serum albumin. Refolding within each domain.

Antiserum to bovine serum albumin was fractionated into populations of antibody directed against party, an apparent pathway of refolding within each domain was obtained which is consistent with the proposed evolutionary pathway of the albumin molecule. The COOH-terminal one-third of each domain refolds faster than the NH2-terminal two-thirds of each respective domain. In addition, further evidence in given for a correlation between the rate of refolding and the degree of interdomain influence that might restrict refolding.

Amino Acids↗
PubMed1977

Suppressor cells in tolerance to HGG: kinetics and cross-suppression in high dose tolerance--absence in low dose tolerance.

Spleen cells from mice made tolerant with high doses of human gamma-globulin (HGG) specifically suppress the immune response of normal, syngeneic, spleen cells. These suppressor cells were found to be cross-reactive in that they would suppress the immune response of normal spleen cells to bovine gamma-globulin (BGG) as well as to HGG. In contrast, suppressor cells could not be demonstrated in spleens of mice made tolerant with low doses of HGG (i.e., T-cell tolerance), nor could they be found in high dose tolerant mice following a second injection of DHGG at a time when the initial suppressor activity had waned. The role of suppressor cells in the induction, maintenance, and loss of tolerance is discussed.

Animals↗
PubMed1977

Neonatally induced tolerance to HGG: duration in B cells and absence of specific suppressor cells.

A specific, long lasting, tolerant state to human gamma-globulin (HCG) was established in neonatal A/J mice. These suckling mice received the tolerogen in the colostrum of their mother who had been injected with DHGG. The tolerant state could not be accounted for by "factors" other than HGG in the colostrum. The duration of this tolerance in the intact animal and in the B cell population was 16 to 18 weeks. Naturally occuring nonspecific suppressor cells were evident but specific suppressor cells could not be demonstrated. These results are discussed in relation to possible mechanisms of the induction of tolerance to self.

Animals↗
PubMed1976

Antibody as an immunological probe for studying the refolding of bovine serum albumin. I. The catalysis of reoxidation of reduced bovine serum albumin by glutathione and a disulfide interchange enzyme.

We have used an immunochemical approach to study the refolding of bovine serum albumin. Using antibody as a probe for return of native structure, we have been able to demonstrate the regeneration of native structure at several sites on the surface of the molecule. Using this technique, we have shown that the rate of refolding of reduced bovine serum albumin catalyzed by either glutathione or rat liver disulfide interchange enzyme is greater than the rate of air reoxidation of albumin. The half-regeneration times for albumin, however, are substantially greater than those obtained with smaller proteins that have fewer disulfide bonds. We have also demonstrated that the reoxidized monomers isolated at the end of the refolding process are immunologically identical to native monomers. In addition, the tryptophan fluorescence emission maxima were the same as that of the native monomers.

Antibodies↗
PubMed1976

Antibody as an immunological probe for studying the refolding of bovine serum albumin. II. Evidence for the independent refolding of the domains of the molecule.

Antiserum to bovine serum albumin were used as a probe for native structure to study the process of refolding of denatured bovine serum albumin. Different antigenically active fragments that represent domains and subdomains of the molecule were isolated. Restricted populations of antibody to albumin were obtained by fractionating antisera to the native intact molecule on immunoadsorbents bearing these fragments. The restricted antibody populations were then used to probe the surface of the molecule during the refolding process. Some regions of the molecule refolded more rapidly than other regions. Isolated domains of albumin also refolded to native antigenic structure demonstrating that the entire polypeptide chain was not necessary for reformation of native structure. However, there does seem to be some interdomain influence on the rate of refolding of a particular domain within the intact protein.

Amino Acids↗
PubMed1976

Induction of immunologic tolerance in nursing neonates by absorption of tolerogen from colostrum.

Deaggregatedhuman gamma-globulin (DHGG) injected into female mice within 24 hr after delivery of a litter enters the colostrum and is absorbed intact through the intestine by nursing neonates. This absorbed HGG was present in the neonatal circulation at concentrations of 0.3 to 0.6 mg/ml of serum under the experimental conditions used. This absorption of HGG by the nursing neonate resulted in a complete, specific, tolerant state to HGG. This tolerant state was stable upon adoptive cell transfer and could not be abrogated by transfer of normal syngeneic spleen cells.

Absorption↗
PubMed1975

Evidence for specific suppression in the maintenance of immunologic tolerance.

Specific suppressor cells have been demonstrated in mice tolerant to the thymus-dependent antigen HGG. Transfer of normal thymocytes, normal spleen cells, or immune spleen cells into these tolerant mice did not restore immunocompetence to HGG. Furthermore, the transfer of tolerant spleen cells into normal recipients abrogated the response of these recipients to subsequent challenge with immunogenic HGG. Spleen cells removed from mice 5, 8, or 11 wk after the induction of tolerance specifically suppressed the response of normal spleen cells in an adoptive cell transfer system. The extent of suppression appears to be dependent upon how long after the induction of tolerance the cells were removed from the tolerant donors and how soon after transfer the recipients were challenged.

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