Activation of immune system effector function by T-cell or Fc receptor intracellular domains.
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Amino Acid Sequence↗
Biomedical subjects
M Amiot
Publications and source records attributed to M Amiot.
Expression of the Blast-1 activation/adhesion molecule and its identification as CD48.
We have analyzed the induction and expression of Blast-1 at the mRNA and protein levels and demonstrated its identity with CD48. Blast-1/CD48 is expressed on a wider range of cell types, notably T cells and monocytes, than previously thought, but appears to be restricted to lymphoid and myeloid cells. Resting B and T cells express Blast-1/CD48 molecules at the cell surface; however, they lack the epitope recognized by the 17D6 mAb. Resting B cells express no detectable Blast-1/CD48 mRNA. Induction by EBV infection or stimulation with PMA, IL-4, or PHA results in increased levels of Blast-1/CD48 protein (both 6.28 and 17D6 epitopes) at the cell surface. Detailed analysis of EBV-induced expression revealed that it is due to increased steady-state levels of Blast-1/CD48 mRNA induced by transforming but not nontransforming strains of the virus. Induction by IL-1 beta, ionomycin, or suboptimal levels of PMA plus ionomycin results in increased expression of the 17D6 epitope only. In transfected Cos-7 cells Blast-1/CD48 at the cell surface expresses only the 6.28 epitope, whereas cytoplasmic molecules express both 17D6 and 6.28 epitopes. We suggest that these results are most consistent with the idea that Blast-1/CD48 molecules are complexed at the surface of resting cells and Cos-7 cells, resulting in masking of the 17D6 epitope. Activation causes dissociation of the complex, revealing the 17D6 epitope. The existence of 17D6+6.28- Blast-1/CD48 molecules was demonstrated by immunoprecipitation analysis, which also revealed that, unlike the rest of the molecules, this subset was resistant to digestion with glyosylphosphatidylinositol-specific phospholipase C.
Antibodies, Monoclonal↗
The hematopoietic and epithelial forms of CD44 are distinct polypeptides with different adhesion potentials for hyaluronate-bearing cells.
CD44 is a polymorphic integral membrane protein which recognizes hyaluronate and whose proposed roles encompass lymphocyte activation, matrix adhesion and the attachment of lymphocytes to lymph node high endothelial venules (HEVs). Immunochemical and RNA blot data have supported the existence of two forms of CD44: a hematopoietic form expressed by cells of mesodermal origin (and by some carcinoma cell lines) and an epithelial form weakly expressed by normal epithelium but highly expressed by carcinomas. This report describes the isolation of a cDNA encoding a distinct CD44 polypeptide expressed by epithelial cells. Re-expression of each form of CD44 in a B cell line allowed cells transfected with the hematopoietic but not the epithelial form to bind to viable rat lymph node HEV cells in primary culture.
Amino Acid Sequence↗
Identification and analysis of cDNA clones encoding CD53. A pan-leukocyte antigen related to membrane transport proteins.
CD53 is a human cell-surface Ag expressed exclusively by nucleated cells of hemopoietic origin. In this work a cDNA clone encoding the CD53 Ag was isolated from a COS cell-expression library. The sequence of the cDNA predicts a protein of 219 residues bearing four putative membrane-spanning hydrophobic domains. Sequence analysis shows that CD53 is related to three other recently described molecules: a melanoma Ag, ME491; a B cell Ag, CD37; and the broadly distributed hemopoietic cell Ag S5.7. Comparison of NH2-terminal protein sequence of OX44 rat Ag and CD53 suggest that CD53 is the human homologue of OX44. In addition, CD53 is distantly related to Escherichia coli lac Y permease, a type III integral membrane protein that ferries lactose into the bacterial cell. CD53 transcripts increase in prevalence after mitogenic stimulation, suggesting that the protein may be involved in the transport of factors essential for cell proliferation.
Amino Acid Sequence↗
Correlation between T cell receptor gamma delta isotypic forms and cytotoxic activity: analysis with human T cell clones and lines.
Three biochemically distinct isotypic forms of the human T cell receptor (TcR) gamma delta structure can be expressed at the cell membrane. This unique variation in structure of TcR, which is due to C gamma gene segments utilization, prompted us to look for isotype-association functional differences. In this regard, we have developed human T cell clones or lines from normal thymus or peripheral blood from several patients. In the present report, we have selected by phenotypic, biochemical, and TcR gene rearrangement analysis representative pairs of IL2-dependent clones or lines for each TcR gamma delta isotypic form. The results showed a lack of correlation between the TcR isotypes and the ability of the cells to proliferate in response to TcR stimulation mediated through the CD3 molecular complexes. By contrast, despite the fact that all of these representative cells exhibit an NK-like activity, as measured by their ability to kill K562, the strongest lytic activity was observed with the cells having the disulfide-bonded form of the receptor. Moreover only those latter cells were able to efficiently kill the LAK-sensitive Daudi cell line.
Clone Cells↗
K20 and ICO-10 monoclonal antibodies (gp120/200; Thy-1): immunophenotyping of human solid tumours.
Solid tumour cells were shown to express VLA-beta and Thy-1 antigens. For identification of these molecules two monoclonal antibodies, K-20 and ICO-10, characterised in detail previously, were used. Four groups of solid tumours have been identified according to their immunophenotype: VLA-beta+ and Thy-1-; VLA-beta+ and Thy-1+; VLA-beta- and Thy-1+; VLA-beta- and Thy-1-. To a certain extent these groups have been shown to reflect tumour histogenesis: tumours of epithelial origin never expressed an ICO-10+, K20-phenotype while soft tissue sarcomas and neuroblastoma cells never expressed the beta-chain of VLA molecular complexes.
Antibodies, Monoclonal↗
A lymphocyte molecule implicated in lymph node homing is a member of the cartilage link protein family.
Monoclonal antibodies in the Hermes family recognize a lymphocyte structure that participates in lymphocyte adhesion to endothelium and has been suggested to be the human homolog of the murine Mel-14 lymph node homing receptor. Recently, antibodies against the Hermes antigen, the polymorphic glycoprotein Pgp-1 antigen, and the broadly expressed CDw44 antigen have been shown to recognize the same structure. In this work, cDNA clones encoding the CDw44 antigen were isolated and expressed in COS cells. Two forms were identified: a lymphoid form expressed in hematopoietic cells, and an epithelial form weakly expressed in normal epithelium but highly expressed in carcinomas. The extracellular domain of CDw44 bears homology to cartilage link proteins and a related segment of proteoglycan core protein. However, comparison with the recently identified sequence of the Mel-14 antigen shows that CDw44 and Mel-14 are unrelated.
Amino Acid Sequence↗
A surface glycoprotein complex related to the adhesive receptors of the VLA family, shared by epidermal Langerhans cells and basal keratinocytes.
A murine monoclonal antibody, designated K20, was raised by immunization with a human malignant T-cell line. It reacted specifically with membrane glycoprotein complexes on early haematopoietic cells, T cells, and monocytes. In epidermis, K20 specifically reacted with Langerhans cells and basal keratinocytes, as demonstrated by double labeling experiments. Membrane immunoprecipitation analysis demonstrated that the antigen identified by K20 on lymphoid cells and epidermal cells was different. While on lymphoid cells, K20 recognized glycoprotein complexes made of a constant 130-kD subunit associated with subunits of higher molecular weight ranging from 150 to 200 kD, a complex of 105-145 kD was precipitated from Langerhans and basal cells. Metabolic labeling studies demonstrated that these proteins were synthesized by the basal cells. The antigen identified by K20 was thought to belong to the integrins, a family of cell surface receptors that play a role in cell adhesion, cell interactions, wound healing, and immune defense mechanisms. K20 is the first monoclonal antibody that specifically recognizes a membrane antigen common to Langerhans and basal cells. Additionally, K20 is the first of five reported monoclonal antibodies to have been characterized on the epidermal cells that detect antigens shared by lymphoid subpopulations and normal basal keratinocytes.
Antibodies, Monoclonal↗
Intermolecular complexes between three human CD1 molecules on normal thymus cells.
The first cluster of differentiation (CD1) defines at least three distinct human thymic cell-surface differentiation antigens-CD1a, CD1b, and CD1c. We looked for structural homology of the three CD1 heavy chains at their peptide level by two-dimensional peptide maps. We show here that the CD1a Mr 49,000 heavy chain and the CD1b Mr 45,000 heavy chain appear to be more homologous to each other than to the CD1c Mr 43,000 heavy chain and that only one tyrosil peptide is common to the three heavy chains. Study of the CD1 heavy chains from several individuals reveals a very limited polymorphism of these molecules. We also demonstrate here that CD1a or CD1a-like molecules and other CD1 molecules can form intermolecular complexes on the surface of normal thymus cells. Molecules that are structurally very similar to CD1a molecules are associated noncovalently either with CD1c molecules or with CD1b molecules, and only CD1a molecules can associate covalently with CD8 molecules. In contrast, we could not find these intermolecular complexes on the surface of leukemic T-cell lines in culture.
Antibodies, Monoclonal↗
HLA class I molecules are associated with CD1a heavy chains on normal human thymus cells.
The molecules encoded by the major histocompatibility complex play a pivotal role in regulatory interactions between cells of the immune system, which can result in the activation and function of T cells. The function of the CD1 molecules, which are homologous to the major histocompatibility complex-encoded molecules but are encoded on human chromosome 1, is not known. HLA class I molecules and CD1a heavy chains share the ability to associate with several different cell-surface molecules. We show here, by several technical approaches, that HLA class I molecules are associated with CD1a heavy chains on the surface of normal thymus cells. The functional significance of this association during T-cell differentiation is discussed.
Antibodies, Monoclonal↗
Analysis of CD1 molecules on thymus cells and leukemic T lymphoblasts identifies discrete phenotypes and reveals that CD1 intermolecular complexes are observed only on normal cells.
We looked at the surface expression of the three distinct human thymic cell surface differentiation antigens, CD1a, CD1b, and CD1c, that presently define the first cluster of differentiation (CD) on the cells from 34 patients with acute T cell malignancies. We also studied the expression of other T cell-restricted molecules, including the T cell receptors, on these cells. Our results confirm the extensive phenotypic heterogeneity of the cells from acute T cell malignancies, which contrast with the more limited phenotypic diversity of subacute or chronic T cell malignancies. Our study of normal children and fetal thymus cells shows that the extensive phenotypic heterogeneity of the malignant cells reflects the heterogeneity of the thymic subpopulations and shows that most of the phenotypes observed on malignant T cells have a normal counterpart, particularly in the fetal thymus. Moreover, we demonstrate that the CD1a molecules, which can form three different types of noncovalent intermolecular complexes on the surface of normal thymus cells, do not form any noncovalent intermolecular complexes on the surface of leukemic cells. We also show that CD1a molecules can form covalent intermolecular complexes with CD8 molecules on some but not all malignant cells.
Antibodies, Monoclonal↗
Heterogeneity of the first cluster of differentiation: characterization and epitopic mapping of three CD1 molecules on normal human thymus cells.
In humans, the presence of two non-HLA class 1-like molecules, whose expression, similar to murine Tla, is restricted to cortical thymocytes, has been shown with monoclonal antibodies defining the first cluster of differentiation (CD1). We report here with the use of 12 anti-CD1 antibodies and a combination of technical approaches, the characterization of a third CD1 molecule. We show that we can presently define seven different epitopes on the three CD1 molecules: four epitopes are restricted to the 49,000 dalton molecule, two epitopes to the 45,000 dalton molecule, and one epitope to the 43,000 dalton molecule. We show that the association of the newly identified 45,000 dalton heavy chain with human beta2-microglobulin is weak. In addition we show the presence of a fourth non-HLA class I molecular species on the surface of normal human thymus cells.
Animals↗
The human cell surface glycoprotein complex (gp 120,200) recognized by monoclonal antibody K20 is a component binding to phytohaemagglutinin on T cells.
Monoclonal antibody K20 recognizes a human glycoprotein complex that is not restricted to haematopoietic lineages but is preferentially expressed on early haematopoietic cells, T cells, and monocytes. This glycoprotein complex is made of a constant 120,000-140,000 Mr subunit noncovalently associated at the cell surface with subunits of higher Mr ranging from 150,000 to 200,000 on different cell types. Internal labelling with [35S]methionine and pulse-chase experiments revealed that in the cell the 120,000 Mr glycoprotein of this complex is also noncovalently associated with a 100,000 Mr glycoprotein, and that both glycoproteins are independently biosynthesized. This glycoprotein complex is shown by immunoprecipitation by lectin plus antilectin antibodies and by sequential immunoprecipitations to be one of the cell surface structures bound by phytohaemagglutinin on the surface of normal T cells.
Animals↗
A novel human leukocyte differentiation antigen: monoclonal antibody anti-D44 defines a 28 Kd molecule present on immature hematologic cells and a subpopulation of mature T cells.
Anti-D44 is a cytotoxic IgG2b monoclonal antibody (MAb), which reacts with two polypeptides of 28 and 30 Kd from human peripheral T cells after western blotting. The antigen is present in low density on bone marrow cells from the myeloid lineage, probably including most CFU-GM; the antigen is present on megakaryocytes but is not detectable on erythroid cells as well as pre-B and B cells. Growth of BFU-E appears to be partially inhibited after treatment with anti-D44 + complement, an effect that should be due to bone marrow T cells rather than to BFU-E destruction. With maturation, the antigen is barely detectable on mature polymorphonuclear neutrophils, and is not detectable on platelets and monocytes. In contrast, cells from the thymic cortex carry a high density of this molecule; medullary thymocytes carry a low density. Large thymocytes ("thymoblasts") distinct from epithelial or interdigitating cells also bear a high density of the antigen. In the periphery, a subpopulation of T cells displays a high density of D44 molecules. D44 antigenic density is not linked to cell growth or to T cell activation. Double labeling and cell sorting experiments have shown that 40% of E rosette-forming cells are D44(+)-CD4+, 10% are CD8(+)-D44+ and 10% are CD4(-)+CD8-, CD2+. In an accompanying report, correlation is shown between expression of the D44 defined molecule on T cell subpopulations and the function they exert. Immunoperoxidase studies of skin, brain, and kidney tissues, facilitated by the fact that the antigen is resistant to inclusion in Epon, which permits staining of semi-thin sections, have not revealed any positive nonhematologic cell.
Animals↗