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Biomedical subjects

C Terhorst

Publications and source records attributed to C Terhorst.

At least 181 records · Page 10Linked to original sources
PubMed1983

Biochemical comparison of the T6 antigen and HLA-A,B antigens.

The human thymic differentiation antigen T6, which was found to be associated with beta 2-microglobulin, was compared to the HLA-A,B antigens. Using a heteroantiserum prepared against denatured heavy chains of HLA-A,B antigens, no cross-reactivity with denatured T6 could be detected. The molecular weight of the protein backbone of T6 was found to be 34,000 as compared to 40,000 for the HLA-A,B antigens. Also, not only was the percentage of carbohydrate of T6 (25-35%) different from the HLA-A,B antigens (10%), but lectin binding studies showed that their sugar composition may differ. The two forms of T6, which previously had been found on MOLT-4 cells, appeared to have different levels of glycosylation, but apparently had the same protein backbone. T6, like HLA, has a hydrophobic domain, since it could be labeled with [125I]iodonaphthylazide. We conclude from these studies that T6 may be a class I MHC antigen which is different from the classical HLA-A,B antigens.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1983

Comparison of target antigens of monoclonal reagents OKT5, OKT8, and Leu2A, which inhibit effector function of human cytotoxic T lymphocytes.

The OKT8 antigen, which is present on a subset of thymocytes and peripheral blood T lymphocytes, was examined utilizing a variety of biochemical techniques. It is shown to be a glycoprotein of 34 kD molecular weight which contains a hydrophobic region. Further, under nonreducing conditions, dimers of 76 kD and 67 kD are found. These species are most likely generated by differences in internal disulfide bonding. When two previously described antigens, OKT5 and Leu2A, were compared with OKT8, no structural differences could be found among the three antigens. Evidence is presented, however, which indicates that the three monoclonals recognize different epitopes on the molecule. Functional analysis on cytotoxic T lymphocyte (CTL) clones confirmed the biochemical findings concerning the identity of the three proteins.

Antibodies, Monoclonal↗
PubMed1983

Target antigen of monoclonal reagent S5.7: comparison with T3 antigen.

S5.7 recognizes a 20 kD cell surface protein which is present on T lymphocytes. S5.7 binds to a nonglycosylated protein, which can be labeled by cell-surface radioiodination and by a hydrophobic reagent [125I]-iodo-5-naphthyl-1-azide (INA). As the T-lymphocyte-specific T3 complex was found to contain a nonglycosylated 20 kD species, and since this 20 kD T3 form can be labeled preferentially by INA, a comparison between T3 and S5.7 was made. Isoelectric focusing experiments showed, however, that the two proteins are different. Moreover, the S5.7 monoclonal antibody does not block CML, is not mitogenic, reacts with immature cells of several hemopoietic lineages, and differs in that respect from anti-T3 monoclonal antibodies.

Antibodies, Monoclonal↗
PubMed1983

Characterization of monoclonal antibodies against cell surface molecules associated with cytotoxic activity of natural and activated killer cells and cloned CTL lines.

Supernatants of hybridomas from fused spleen cells of mice immunized with either a T4+ or a T8+ CTL clone, were screened for their ability to inhibit the cytotoxic activity of the T4+ and the T8+ CTL clone. Eight monoclonal antibodies (MAbs) with blocking activity were obtained and a preliminary characterization of these antibodies was carried out. The MAbs SPV-L1 and SPV-L5 were found to react with thymocytes and all peripheral blood leukocytes. SPV-L1 and SPV-L5 precipitated a molecular complex consisting of two noncovalently bound chains of molecular weights of 95 and 160 kD indicating that they recognize the human equivalents of the recently described leukocyte function associated (LFA-1) antigens. The SPV-L1 and SPV-L5 antibodies inhibited the reactivity of six CTL clones tested in this study. In addition, SPV-L1 and L5 blocked the lectin dependent cellular cytotoxicity mediated by these CTL clones. Natural killer cell activity mediated by fresh peripheral blood lymphocytes and activated killer cell activity generated in MLC both measured against K562 was also inhibited by SPV-L1 and SPV-L5. Two other antibodies, SPV-L3 and SPV-L4 blocked strongly the cytotoxic activity of two T4+ CTL clones, whereas the reactivity of the three T8+ CTL clones and one T4+ CTL clone was not or only moderately inhibited. These antibodies recognized an Ia antigen as judged from tissue distribution and immunoprecipitation studies. However, these latter studies also suggest that SPV-L3 and SPV-L4 recognize HLA-DC rather than HLA-DR antigens. Finally, three antibodies (SPV-T3a, SPV-T3b, SPV-T3c) were obtained directed against the T3 molecular complex and one MAb (SPV-T8) was found to react with T8. The anti-T3 reagents were shown to be mitogenic for peripheral blood lymphocytes, with the exception of SPV-T3a. The results presented here indicate that the antigens recognized by SPV-L1 and SPV-L5 are involved in various cytotoxic reactions. In contrast, SPV-L3, SPV-T3 and SPV-T8 only seem to play a role in antigen specific cytotoxic reactions.

Animals↗
PubMed1983

Localization of a gene controlling the expression of the human transferrin receptor to the region q12 leads to qter of chromosome 3.

A monoclonal antiserum, 66-IG10, raised against human thymocytes was found to be directed against the human transferrin receptor. A panel of human X Chinese hamster somatic cell hybrids, in conjunction with the 66-IG10 reagent, was used to assign the gene(s) coding for the transferrin receptor to the q12 leads to qter region of human chromosome 3.

Animals↗
PubMed1983

The thymic differentiation markers T6 and M241 are two unusual MHC class I antigens.

The human beta 2-microglobulin (beta-2m)-associated human thymocyte differentiation antigens T6 and M241 were compared using biochemical techniques. T6 and M241 antigens reside on different molecules with apparent m.w. of 49,000 and 43,000, respectively. Here we show that both proteins have a protein backbone m.w. of 33,000. In addition, T6 and M241 have a large portion of their peptides in common. When we compared the protein backbone m.w. of T6 and M241 with the murine beta-2m-associated thymus leukemia (TL) antigens, we found a considerable difference in size, suggesting that T6 and M241 may not be human homologues of TL antigens and constitute a novel type of major histocompatibility (MHC) class I antigens.

Animals↗
PubMed1983

Human natural killer cells analyzed by B73.1, a monoclonal antibody blocking Fc receptor functions. II. Studies of B73.1 antibody-antigen interaction on the lymphocyte membrane.

In this paper, we characterize the antigen recognized by the monoclonal antibody B73.1 and the modification occurring at the membrane of the positive cells after interaction with the antibody. The B73.1-defined antigen is a protein of 50,000 to 72,000 daltons that is sensitive to pronase but not to trypsin treatment. B73.1 antibody, and its F(ab')2 fragment, directly block, at high concentrations, the binding of IgG antibody-sensitized erythrocytes to the Fc receptors (FcR) of a subpopulation of lymphocytes and neutrophils. B73.1 antibody dissociates rapidly from the positive cells, but concomitant modulation of both B73.1 antigen and FcR is induced when cells are incubated in the continuous presence of antibody or when B73.1 antibody is cross-linked at the cell membrane with an anti-mouse immunoglobulin antiserum. Reaction of lymphocytes with immune complexes also induces modulation of both FcR and B73.1 antigen, without affecting the expression of other antigens on the positive cells. The possibility that the antigen is internalized and digested by the cell after reaction with the antibody is discussed. B73.1 antibody inhibits antibody-dependent cytotoxicity mediated by lymphocytes (K cells) and neutrophils, whereas it does not affect spontaneous cytotoxicity of NK cells. These results suggest the B73.1-defined antigen might be the FcR or a structure closely related to it on K/NK cells.

Antibodies, Monoclonal↗
PubMed1983

Differentiation antigens of human hemopoietic cells: patterns of reactivity of two monoclonal antibodies.

Two mouse anti-human monoclonal antibodies (S3.13 and S5.7) raised against cells of acute myelogenous leukemia were found to react with antigens expressed on the surface of subsets of monocytes and lymphocytes. S3.13 precipitates a peptide of Mr 29,000, and S5.7 precipitates a peptide of Mr 20,000 present on the surface of all the cell types tested. These two surface antigens were distributed on discrete subpopulations of normal hemopoietic cells. The antibodies reacted with all (S5.7) or a subpopulation (S3.13) of peripheral blood T-lymphocytes, and with a subset of monocytes. Both antibodies reacted with bone marrow blast cell progenitors of the myelomonocytes and erythroid lineage. S5.7 also reacted with non-T-lymphocytes and with cells of the eosinophilic lineage. Both antigens disappeared from the cell surface during normal myeloid and erythroid differentiation. Thus, these monoclonal antibodies define the molecular characteristics and the cellular distribution of two differentiation antigens present on cells of the hemopoietic lineage.

Animals↗
PubMed1982

Structural analysis of differentiation antigens Mo1 and Mo2 on human monocytes.

Mo1 and Mo2 are membrane differentiation antigens expressed by human monocytes, and in the case of Mo1, by granulocytes and null cells. Mo1 antigen expression is resistant to protease treatment of intact monocytes while Mo2 is protease sensitive; Mo2 antigenic activity is regenerated by trypsin-treated monocytes during culture under conditions that favor protein synthesis. Further biochemical analysis reveals that Mo1 is associated with a glycoprotein consisting of two subunits of 94,000 and 155,000 MW. Mo2 resides on a glycoprotein of 55,000 MW. Immunoprecipitation of Mo1- and Mo2-bearing structures from lysates of internally labeled cells indicates that these proteins are synthesized by human monocytes.

Antibodies, Monoclonal↗
PubMed1982

Complexity of the human T lymphocyte-specific cell surface antigen T3.

A human T lymphocyte cell surface antigen T3 was found to be involved in several functions that were specific for the cells that express this marker on their surface. We show here that several glycoproteins were found in the immunoprecipitates prepared with a monoclonal reagent anti-T3. In addition to the major glycoprotein complex of 20 kd, glycoproteins of 25 to 28 kd, 37 kd, and 44 kd were detected in immunoprecipitates. The charge heterogeneity of the 20 kd and 25 to 28 kd proteins was caused by variable sialic acid content. The 20-kd T3 glycoprotein carried several "complex-type" and endoglycosidase-H-sensitive sugar moieties. We found that the 20-kd protein could be labeled with 125I-iodonaphthylazide, a reagent that reacts with hydrophobic areas of proteins.

Acetylglucosaminidase↗
PubMed1982

Further biochemical characterization of the human thymocyte differentiation antigen T6.

Charge heterogeneity of the human thymocyte antigen T6 was studied by isoelectric focusing and two-dimensional gel electrophoresis. The larger subunit of T6 (a 49,000 m.w. glycoprotein) contained several oligosaccharide side chains bearing up to 12 terminal sialic acids. When T6 antigens from 19 individual thymuses were analyzed, no differences in the isoelectric focusing patterns of the larger subunit could be detected. The larger subunit of the T6 antigen from MOLT-4 cells (52,000 m.w.) contained an extra oligosaccharide if compared with the T6 antigen from thymus or three other T leukemic cell lines. Two types of small subunits of T6 were found. In addition to a protein of m.w. 12,000, pI 5.5 identified as beta 2-microglobulin, a (m.w. 12,000, pI 7.0) nonglycosylated protein, was detected on two dimensional gels. This protein does not cross-react with beta 2-microglobulin, and its amount varied in different T6 preparations. The tissue distribution, the m.w. the association with beta 2-microglobulin, and the limited structural heterogeneity of T6 support the idea that T6 is the human homologue of the murine thymus leukemia antigen (TL).

Adolescent↗
PubMed1981

Identification of a cell-surface protein involved in the binding site of Sindbis virus on human lymphoblastic cell lines using a heterobifunctional cross-linker.

A cell-surface protein of molecular weight 90000 was identified as the major protein located at or near the binding site of Sindbis virus on the lymphoblastic cell lines JY and Daudi. This Sindbis-virus-binding protein was detected by cross-linking Sindbis virus, modified with 4-[6-formyl-3-azidophenoxy]butyrimidate, to the cell surface. The applicability of this compound in the identification of specific cell-surface proteins was demonstrated using a monoclonal antibody reactive with beta 2-microglobulin, a protein which is associated with the human histocompatibility antigens (HLA-A, HLA-B, HLA-C).

Autoradiography↗
PubMed1981

Characterization of T cell surface glycoproteins T 1 and T 3 present on all human peripheral T lymphocytes and functionally mature thymocytes.

The monoclonal antibodies, anti-T1 and anti-T3, both react with all human peripheral thymus-derived lymphocytes and with 10% of thymocytes; each, however, recognizes different cell surface structures. It was determined that the target antigen of anti-T is a 69 000 molecular weight cell surface glycoprotein and that the T3 antigen is a 19 000 mol. wt. glycoprotein.

Borohydrides↗