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Biomedical subjects

W van Ewijk

Publications and source records attributed to W van Ewijk.

At least 37 records · Page 2Linked to original sources
PubMed1995

Specific immunologic recognition of the tumor-specific E2A-PBX1 fusion-point antigen in t(1;19)-positive pre-B cells.

The t(1;19) translocation is the most commonly observed chromosomal translocation in childhood acute lymphoblastic leukemia (ALL). Its presence among pre-B cell ALL cases, has been associated with a poor prognosis. Two genes, E2A and PBX1, are involved in this t(1;19) translocation. As a consequence, parts of the E2A and PBX1 genes are fused, resulting in a chimeric E2A-PBX1 gene, encoding chimeric E2A-PBX1 proteins. As such, the amino acid sequence at the fusion site represents a unique tumor-specific determinant. We report on the generation of a polyclonal antiserum, termed BP 1/19, raised against the tumor-specific E2A-PBX1 junction of E2A-PBX1 proteins. The specificity of antiserum BP 1/19 for the E2A-PBX1 fusion-point is demonstrated at the peptide and at the protein level. Furthermore, specific binding of antiserum BP 1/19 to t(1;19) positive cells was shown using immunofluorescence techniques. The study shows that: (1) the tumor-specific fusion-point epitope on E2A-PBX1 proteins is presented in an antigenic fashion, and (2) this particular fusion-point epitope can be used in immunological marker analysis using fluorescence microscopy.

Amino Acid Sequence↗
PubMed1994

Markers of mouse macrophage development detected by monoclonal antibodies.

In this review, we present and discuss a selected panel of antibody-defined markers expressed during different stages of mouse macrophage development. We distinguish four categories of markers, which are characteristic of: (1) macrophage precursors and immature macrophages (ER-MP12, ER-MP20, ER-MP54, ER-MP58); (2) mature macrophages in general (F4/80, BM8, Mac-1, Mac-2, ER-BMDM1); (3) macrophage subsets (ER-HR3, ER-MP23, ER-TR9, Forssman antigen, MOMA-1, MOMA-2, Monts-4, SER-4), and (4) IFN-gamma-stimulated macrophages (H-2Ia, LFA-1, ICAM-1, 158.2, MBR-2, TM-2, TM-4, and TM-5). It should be noted that many of the markers in this last category are inducible by other stimuli as well. The rigid classification of markers into four separate groups should be regarded as a digitalization of a continuum, thus inevitably implicating a simplification of the complex phenotypic changes that occur during mononuclear phagocyte development. Nevertheless, the current selection of antibodies against markers for different developmental stages of macrophages constitutes an important tool for characterization of mouse macrophages which participate in various biological processes.

Animals↗
PubMed1994

New monoclonal antibodies against the putative immunosuppressive site of retroviral p15E.

Both retroviral infections as well as human tumors may cause immunosuppression. One of the factors involved in immunosuppression in patients with squamous cell carcinoma of the head and neck (SCC-HN) is a protein related to the retroviral protein p15E. A conserved, 17-amino acid sequence represents the immunosuppressive epitope of retroviral p15E. In order to study the relationship between SCC-HN associated immunosuppression and retroviral p15E, we produced three new monoclonal antibodies (MAbs; ER-IS1, ER-IS2, and ER-IS5) directed against the immunosuppressive synthetic CKS-17 peptide. These MAbs react with the immunosuppressive peptide (in enzyme-linked immunosorbent assay), with human tumor cell lines (in FACScan analysis), with retroviral p15E (on Western blot), and with cryostat sections of SCC-HN tumor tissue. In addition, the MAbs neutralize the immunosuppressive low molecular weight factors present in sera of patients with SCC-HN. These results show that retroviral p15E and the immunosuppressive factors associated with SCC-HN share a conserved immunosuppressive epitope and that MAbs against this epitope can be used for detection and neutralization of the tumor-associated immunosuppressive protein(s).

Amino Acid Sequence↗
PubMed1994

Distinct mouse bone marrow macrophage precursors identified by differential expression of ER-MP12 and ER-MP20 antigens.

The characterization of early branch points in the differentiation of leukocytes requires identification of precursor cells in the bone marrow. Recently, we produced two monoclonal antibodies, ER-MP12 and ER-MP20, which in two-color flow-cytometric analysis divide the murine bone marrow into six defined subsets. Here we show, using fluorescence-activated cell sorting followed by macrophage colony-stimulating factor-stimulated culture in soft agar, that precursors of the mononuclear phagocyte system reside only within the ER-MP12hi20-, ER-MP12+20+ and ER-MP12-20hi bone marrow subsets. Together, these subsets comprise 15% of nucleated bone marrow cells. Furthermore, we provide evidence that the macrophage precursors present in these subsets represent successive stages in a maturation sequence where the most immature ER-MP12hi20- cells develop via the ER-MP12+20+ stage into ER-MP12-20hi monocytes.

Animals↗
PubMed1994

Inhibition of proliferation and differentiation during early T cell development by anti-transferrin receptor antibody.

Proliferating cells require iron and, therefore, express the transferrin receptor (CD71) that mediates cellular iron uptake. Cycling thymocytes, which have the CD4-8-3-, CD4-8+3-, or CD4+8+3- phenotypes, also express CD71. The importance of CD71-mediated iron uptake for proliferation and maturation of thymocytes was studied using fetal thymus organ cultures at day 14 of gestation and treating them for 7 days with a CD71 monoclonal antibody (mAb). The intracellular iron deficiency caused by this treatment, inhibits both proliferation and maturation of the thymocytes. Cell recovery was reduced by 60%, but cells still expanded tenfold during the culture. Remarkably, the final maturation of alpha beta T cells was completely blocked as no thymocytes with low or high CD3/alpha beta TcR expression developed. Moreover, only few cells reached the CD4+8+3- stage of T cell development. CD4-8-3- thymocytes, however, as well as its CD44-25+ subset developed in normal numbers, suggesting that CD44-25+ CD4-8-3- cells, or their immediate progeny, were most vulnerable to CD71 mAb treatment. The development of gamma delta T cells, which also express CD71, was not affected in these cultures. This suggests that gamma delta T cells are either less iron-dependent or possess alternative iron-uptake mechanisms. Thus, our observations indicate that CD71 treatment, causing decreased intracellular iron levels, severely inhibits the major proliferation phase from the CD44-25+ CD4-8-3- to the CD4+8+3- cells, and completely abrogates the final maturation of CD4+8+3- cells into alpha beta TcR-expressing cells. In contrast, proliferation and differentiation of the earliest thymic precursors into CD44-25+ CD4-8-3- cells is not affected by CD71 treatment.

Animals↗
PubMed1994

Transferrin receptor expression as a marker of immature cycling thymocytes in the mouse.

Dividing cells require iron and, therefore, express the transferrin receptor (CD71) on the cell surface to enable internalization of transferrin-bound iron. Since early T cell development is marked by intense proliferation, we questioned whether CD71 might serve as a marker of immature T cells. Therefore, we analyzed the expression of CD71 on fetal, neonatal, and adult thymocytes in correlation with cell size, cell cycle status, and expression of CD3, CD4, CD8, alpha beta TcR, and gamma delta TcR. Phenotypic analysis showed that only the large, immature CD4-8-3-, CD4-8+3-, and CD4+8+3- cells in fetal, neonatal, and adult thymus expressed CD71. In addition, DNA analysis showed that all CD71+ large adult thymocytes were cycling. Downregulation of CD71 occurs when proliferation ceases, i.e., within the CD4+8+3- thymocyte subpopulation. The gradual changes in size and CD71 expression suggest a sequential development within this CD4+8+3- subpopulation from large CD71+ via small CD71+/- to small CD71- cells. As a consequence, CD71 expression is downregulated, in adult T cell development as well as in ontogeny, before the alpha beta TcR appears on the cell surface of the thymocyte. Together, our findings show that CD71 is a marker of immature, proliferating T cells.

Animals↗
PubMed1994

The ER-TR4 monoclonal antibody recognizes murine thymic epithelial cells (type 1) and inhibits their capacity to interact with immature thymocytes: immuno-electron microscopic and functional studies.

The thymic stroma is heterogeneous with regard to cellular morphology and cellular function. In this study, we employed the monoclonal antibody ER-TR4 to characterize stromal cells at the ultrastructural level. To identify the labelled cell type, we used two techniques: immunogold labelling on ultrathin frozen sections and immunoperoxidase staining on thick "vibratome" sections. ER-TR4 reacted with thymic Type 1 epithelial cells (according to our classification). A dense labelling appears in the cytoplasm of cortical cells using the two techniques. Immunogold labelling identified small cytoplasmic vesicles whereas the cytoplasm and the cell membrane seem to be labelled with the immunoperoxidase technique. ER-TR4 also identified isolated thymic nurse cells (TNC), and was observed in vitro to inhibit the capacity of some type 1 epithelial cells to establish interactions with immature thymocytes. This finding supports the hypothesis that the factor is involved in the formation of lymphoepithelial interactions within thymic nurse cells, and thus in the relations that immature thymocytes establish with the thymic microenvironment.

Animals↗
PubMed1994

Crosstalk in the mouse thymus.

The development of mature T cells within the thymus is dependent upon intact cortical and medullary microenvironments. In turn, thymic microenvironments themselves are dependent on lymphoid cells to maintain their integrity. Here, Willem van Ewijk and colleagues discuss experiments that have established the phenomenon of 'crosstalk' within the mouse thymus and suggest a mechanism whereby lymphoid and stromal cells influence each other in a consecutive manner during T-cell development.

Animals↗
PubMed1994

Recognition of the ALL-specific BCR-ABL junction in P190bcr-abl by monoclonal antibody ER-FP1.

The pH chromosome, resulting from the t(9;22) translocation, is the most frequently observed cytogenetic aberration in acute lymphoblastic leukemia (ALL). Two genes, bcr and abl, are involved in this translocation. As a consequence, parts of the bcr and abl genes are fused, resulting in chimeric bcr-abl genes encoding chimeric BCR-ABL proteins. Three bcr-abl genes and proteins have been identified: e1-a2 P190bcr-abl, b2-a2 P210bcr-abl, and b3-a2 P210bcr-abl. Since these chimeric proteins only occur in Ph-chromosome-positive leukemic cells, they are by definition tumor-specific markers. Ph-chromosome-positive ALL is correlated with a bad prognosis, therefore the detection of chimeric BCR-ABL proteins is of prime importance in ALL diagnosis. In the present study, we report on the generation of a monoclonal antibody termed ER-FP1, raised against the tumor-specific e1-a2 BCR-ABL junction in P190bcr-abl. We show that ER-FP1 reacts highly specifically with e1-a2 P190bcr-abl in different assays. The reactivity of ER-FP1 with e1-a2 P190bcr-abl in soluble form was analyzed in an immunoprecipitation assay; specificity was confirmed by peptide inhibition studies. Binding of ER-FP1 to e1-a2 P190bcr-abl at the single cell level was detected by using immunofluorescence techniques. Immunological double-staining experiments using ER-FP1 and a monoclonal antibody recognizing all BCR-ABL proteins confirmed the specificity of ER-FP1 for the e1-a2 fusion point.

Adult↗
PubMed1993

ER-MP12 antigen, a new cell surface marker on mouse bone marrow cells with thymus-repopulating ability: I. Intrathymic repopulating ability of ER-MP12-positive bone marrow cells.

We searched for new cell surface markers that allow a positive identification of thymus-repopulating cells in the bone marrow (BM) of the mouse. Recently we raised two rat monoclonal antibodies (ER-MP12 and ER-MP20) that recognize cell surface antigens expressed by mouse haematopoietic progenitor cells, among which are progenitor cells of the macrophage lineage. Here we show that the ER-MP12 antigen, but not the ER-MP20 antigen, is also expressed by BM cells with thymus-repopulating ability. Using ER-MP12 and ER-MP20 in two-colour immunofluorescence analysis six subpopulations of BM cells can be identified. The thymus-repopulating ability of each BM subpopulation was assessed after fluorescence-activated cell sorting and subsequent intrathymic injection into sublethally irradiated Thy-1 congenic recipient mice. Thymus-repopulating activity appeared to be exclusively confined to two subsets of BM cells expressing either high or intermediate levels of the ER-MP12 antigen, but lacking ER-MP20 antigen expression. These BM subsets comprised 1-2% and 30% of total nucleated BM cells respectively. The frequency of thymus-repopulating cells was maximal in the minor BM subpopulation with the highest level of ER-MP12 antigen expression. We conclude that ER-MP12 detects a hitherto unknown cell surface marker expressed by BM cells with thymus-repopulating ability.

Animals↗
PubMed1993

ER-MP12 antigen, a new cell surface marker on mouse bone marrow cells with thymus-repopulating ability: II. Thymus-homing ability and phenotypic characterization of ER-MP12-positive bone marrow cells.

In the accompanying paper we showed that six distinct subsets of bone marrow (BM) cells can be identified using the mAb ER-MP12 and ER-MP20 in two-colour immunofluorescence analysis. Upon intrathymic transfer into sublethally irradiated mice thymus-repopulating ability was restricted to ER-MP20- BM cells expressing either high or intermediate levels of the ER-MP12 antigen (1-2% and approximately 30% of BM nucleated cells respectively). The highest frequency of thymus-repopulating cells was found in the minor subset of ER-MP12(+)+20- BM cells. In the present study we demonstrate that upon intravenous transfer, thymus-homing and -repopulating BM cells are exclusively confined to the ER-MP12(+)+20- and ER-MP12+20- subpopulations, the highest frequency being detected among ER-MP12(+)+20- BM cells. Analysis of the peripheral blood leucocytes of reconstituted mice showed that not only prothymocytes but also progenitor cells of the B cell lineage as well as the myeloid lineage were present within both subsets. Three-colour flow cytometric analysis revealed that ER-MP12(+)+20- BM cells in particular were phenotypically heterogeneous with respect to the expression of the cell surface markers Thy-1, Sca-1, CD44, B220 and c-kit. Taken together our data demonstrate that ER-MP12 positively identifies BM cells with the ability to home to and repopulate the thymus. The phenotypic heterogeneity displayed by the ER-MP12(+)+20- BM subset, containing the highest frequency of thymus-homing and -repopulating cells, provides a basis for further separation of prothymocyte activity from other haematopoietic activities in the BM of the mouse.

Animals↗
PubMed1993

Detection of tumor-specific antigens in Philadelphia chromosome positive leukemias.

In chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL) the Ph1 chromosome (22q-) is the most frequent chromosomal aberration encountered. At the molecular level the c-abl gene from chr. 9 is translocated to the bcr gene on chr. 22. As a result, a chimeric bcr-abl gene is generated, which encodes chimeric proteins. Since these proteins are only expressed in Ph1 positive cells, they are per definition tumor-specific. In this report we describe the reactivity of polyvalent antisera raised against synthetic peptides corresponding to the tumor-specific bcr-abl junctions. Native chimeric proteins were specifically recognized by these junction-specific antisera. Therefore we conclude that the bcr-abl junctions are antigenically exposed on the chimeric proteins. We discuss the relevance of these antisera for CML and ALL diagnosis.

Amino Acid Sequence↗
PubMed1992

Profound block in thymocyte development in mice lacking p56lck.

The protein Lck (p56lck) has a relative molecular mass of 56,000 and belongs to the Src family of tyrosine kinases. It is expressed exclusively in lymphoid cells, predominantly in thymocytes and peripheral T cells. Lck associates specifically with the cytoplasmic domains of both CD4 and CD8 T-cell surface glycoproteins and interacts with the beta-chain of the interleukin-2 receptor, which implicates Lck activity in signal transduction during thymocyte ontogeny and activation of mature T cells. Here we generate an lck null mutation by homologous recombination in embryonic stem cells to evaluate the role of p56lck in T-cell development and activation. Lck-deficient mice show a pronounced thymic atrophy, with a dramatic reduction in the double-positive (CD4+CD8+) thymocyte population. Mature, single-positive thymocytes are not detectable in these mice and there are only very few peripheral T cells. These results illustrate the crucial role of this T-cell-specific tyrosine kinase in the thymocyte development.

Animals↗
PubMed1992

Antibody recognition of the tumor-specific b3-a2 junction of bcr-abl chimeric proteins in Philadelphia-chromosome-positive leukemias.

The reciprocal translocation between chromosome 9 and chromosome 22, as observed in chronic myeloid leukemia (CML) as well as in acute lymphoblastic leukemia (ALL), results in a 22q- chromosome, the so-called Philadelphia chromosome. The translocation event creates on the Philadelphia chromosome a fusion between two genes: bcr and abl. Depending on the localization of the breakpoint in the bcr gene different chimeric bcr-abl genes are generated, each encoding their own tumor-specific protein: e1-a2P190bcr-abl, b2-a2p210bcr-abl, or b3-a2P210bcr-abl. Especially in ALL, the presence of such a tumor-specific protein is highly associated with a poor prognosis. Detection of these proteins therefore has a strong clinical significance. In this study a polyclonal antiserum, termed BP-2, was raised against a synthetic peptide, corresponding to the tumor-specific 'fusion-point' epitope of the b3-a2P210bcr-abl protein. The specificity of BP-2 for the bcr-abl joining region in b3-a2P210bcr-abl is demonstrated by means of peptide inhibition studies in combination with immunoprecipitation. In addition we show the reactivity of BP-2 with bcr-abl proteins in leukemic cells of a Philadelphia-chromosome-positive ALL patient.

Amino Acid Sequence↗
PubMed1991

CD8 is needed for development of cytotoxic T cells but not helper T cells.

A mutant mouse strain without CD8 (Lyt-2 and Lyt-3) expression on the cell surface has been generated by disrupting the Lyt-2 gene using embryonic stem cell technology. In these mice, CD8+ T lymphocytes are not present in peripheral lymphoid organs, but the CD4+ T lymphocyte population seems to be unaltered. Cytotoxic response of T lymphocytes from these mice against alloantigens and viral antigens is dramatically decreased. Proliferative response against alloantigens and in vivo help to B lymphocytes, however, are not affected. These data suggest that CD8 is necessary for the maturation and positive selection of class I MHC restricted cytotoxic T lymphocytes but is not required on any of the intermediate thymocyte populations (CD8+CD4-TcR- or CD4+CD8+TcRlow) during the development of functional class II MHC restricted helper T cells.

Animals↗
PubMed1991

T-cell differentiation is influenced by thymic microenvironments.

Intrathymic T-cell differentiation requires a symbiotic interaction between thymic microenvironments and developing T cells. This paper attempts to provide insight into lympho-stromal interaction and reviews the architecture of thymic microenvironments, the phenotype of thymic microenvironments, the in vitro culture of thymic microenvironments, and the supportive role of thymic microenvironments in T-cell differentiation. Moreover, we discuss experimental manipulation of thymic microenvironments in vivo and in vitro, using monoclonal antibodies directed to cell surface determinants on stromal cells or their ligands on lymphoid cells. Finally, new types of experimental mouse models are considered with special reference to the role of thymic microenvironments in positive and negative selection of the T-cell repertoire, and the potential influence of T cells on the development of thymic microenvironments.

Animals↗
PubMed1990

Immunologic characterization of the tumor-specific bcr-abl junction in Philadelphia chromosome-positive acute lymphoblastic leukemia.

Philadelphia (Ph')-positive acute lymphoblastic leukemia (ALL) is highly associated with two forms of chimeric bcr-abl proteins: P190bcr-abl and P210bcr-abl. Whereas P210bcr-abl also occurs in chronic myeloid leukemia, P190bcr-abl is uniquely expressed in Ph'-positive ALL. As a consequence, P190bcr-abl is preeminently a tumor-specific marker in leukemic cells of ALL patients. Because P190bcr-abl is composed of the normal bcr and abl proteins, the major part of the P190bcr-abl molecule comprises nontumor-specific determinants. The joining region between bcr and abl, newly generated during the Ph' translocation, is exclusively a tumor-specific epitope on the P190bcr-abl molecule. Therefore, only antibodies against the bcr-abl joining region will detect the tumor-specificity of P190bcr-abl. In this study a polyclonal antiserum, termed BP-ALL, was raised against a synthetic peptide corresponding to the bcr-abl junction in P190bcr-abl. The reactivity of BP-ALL with native P190bcr-abl derived from a Ph'-positive ALL cell line (TOM-1) was tested using immunoprecipitation analysis. BP-ALL reacted highly specifically with P190bcr-abl but not with P210bcr-abl isolated from chronic myeloid leukemia cell lines. Peptide inhibition studies further confirmed the fine specificity of BP-ALL. Our data indicate that the tumor-specific bcr-abl junction domain is exposed in an antigenic fashion on the P190bcr-abl molecule.

Adult↗