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Biomedical subjects

W van Ewijk

Publications and source records attributed to W van Ewijk.

At least 73 records · Page 4Linked to original sources
PubMed1985

[Production of monoclonal antibodies].

Monoclonal antibodies are prepared by a process of somatic cell hybridization. During this process the antibody-forming plasma cells are fused with myeloma cells. Hybrid cells continue to proliferate and to secrete antibodies. Homogeneous cell population which secrete a monoclonal product are obtained by cloning of the hybrid cells. The reactivity of the monoclonal antiserum is then determined by a screening procedure (for example by immunoassay). The principles of the production and the screening of monoclonal antibodies are presented.

Animals↗
PubMed1985

An immunohistologic study of the epithelial and lymphoid components of six thymomas.

Six thymomas were classified histologically and studied immunohistochemically with a panel of mouse and rat monoclonal antibodies directed against thymic epithelial and lymphoid components. The antibodies included monoclonal antibodies directed against cytokeratin, medullary epithelial cells (ER-TR5), and HLA-DR and HLA-ABC antigens, as well as antibodies with specificity for thymocytes. Histologically, one thymoma was characterized by epithelial predominance (EP type), two showed lymphoid predominance (LP type), and two showed mixed lymphoid/epithelial composition (MLE type); one thymoma was a malignant pure epithelial thymoma (PE type). In the thymomas of the MLE and EP types the major populations of cells consisted of HLA-DR-negative, cytokeratin-positive epithelial cells with large ER-TR5-positive subpopulations (i.e., the phenotype of medullary epithelium). In the thymomas of the LP type, the neoplastic population was composed of cytokeratin-positive, ER-TR5-negative cells that expressed the HLA-DR antigen (i.e., the phenotype of cortical epithelium). The thymoma of the PE type consisted of cytokeratin-positive cells, some of which were ER-TR5- and HLA-DR-positive. Double immunofluorescence studies revealed the presence of varying numbers of additional nonepithelial (nonlymphoid) HLA-DR-positive cells in thymomas of the LP, MLE, and EP types. The intervening lymphoid population in the thymomas of the LP, MLE, and EP types consisted largely of cortical thymocytes, as defined by immunologic characterization. These results suggest that thymomas can be classified as medullary or cortical epithelial neoplasms on the basis of their immunologic phenotypes.

Adult↗
PubMed1985

Marginal zone macrophages in the mouse spleen identified by a monoclonal antibody. Anatomical correlation with a B cell subpopulation.

The reactivity of a monoclonal antibody, ER-TR9, that demonstrates heterogeneity among mononuclear phagocytes is described. In the spleen, ER-TR9 exclusively reacts with a population of macrophages located in the marginal zone. ER-TR9 does not react with macrophage antigen 1-positive red pulp macrophages or any other types of splenic stromal cells. ER-TR9+ ve cells localize in anatomical proximity of a subpopulation of B cells, i.e., B cells that are immunoglobulin M positive and weakly positive to negative for immunoglobulin D. The possible significance of this particular interaction between both cell types during the immune response is discussed.

Animals↗
PubMed1985

Repopulation of the mouse thymus after sublethal fission neutron irradiation. I. Sequential appearance of thymocyte subpopulations.

The T cell composition of the thymus of sublethal fission neutron-irradiated CBA/H mice was analyzed with cytofluorometry and immunohistology, using monoclonal antibodies directed to the cell surface antigens Thy-1, T-200, MT-4, Lyt-1, Lyt-2, and MEL-14. The results of this investigation show that whole body irradiation with 2.5 Gy fission neutrons results in a severe reduction and degeneration of the cortex, whereas the medulla is affected to a lesser extent. Irradiation selects, within 24 hr, for a population of dull Thy-1+, bright T-200+, bright Lyt-1+ cells localized in the medulla. Phenotype analysis of the regeneration of the thymus, which starts at about 5 days after irradiation, reveals the sequential appearance of: 1) "null" cells, i.e., lymphoblasts negative for all tested antigens, mainly in the subcapsular area but also in the medulla; 2) Thy-1+ "only" and T-200+ "only" cells in the subcapsular area; 3) Thy-1+, T-200+ cells; and 4) Thy-1+, T-200+, MT-4+, Lyt+ cells in the cortex. In addition, an increased MEL-14 expression is observed in correlation with the expression of Thy-1 and T-200 determinants during the regeneration of the thymus. From day 10 on up to at least 150 days after irradiation, no differences can be observed in the thymus of irradiated and age-matched sham-irradiated control mice, as measured by the expression and distribution of Thy-1, T-200, MT-4, Lyt-1, Lyt-2, and MEL-14 antigens. The observed sequence in phenotype shift in the regeneration of the thymus after irradiation is discussed in view of recently published data on the differentiation of the T cell system.

Animals↗
PubMed1985

Repopulation of the mouse thymus after sublethal fission neutron irradiation. II. Sequential changes in the thymic microenvironment.

The stromal cells of the thymus of sham-irradiated and sublethal fission neutron-irradiated CBA/H mice were analyzed with immunohistology, using monoclonal antibodies directed to I-A and H-2K antigens as well as specific determinants for cortical and medullary stromal elements. In the control thymuses, I-A expression in the thymus shows a reticular staining pattern in the cortex and a confluent staining pattern in the medulla. In contrast, H-2K expression is mainly confluently located in the medulla. Whole body irradiation with 2.5 Gy fission neutrons reduces within 24 hr the cortex to a rim of vacuolized "nurse cell-like" epithelial cells, largely depleted of lymphoid cells. The localization of I-A antigens changes in the cortex and I-A determinants are no longer associated with or localized on epithelial reticular cells. Medullary stromal cells, however, are more or less unaffected. A high rate of phagocytosis is observed during the first 3 days after irradiation. About 5 days after irradiation, the thymus becomes highly vascularized and lymphoid cells repopulate the cortex. The repopulation of the thymic cortex coincides with the appearance of a bright H-2K expression in the cortex which is associated with both stromal cells as well as lymphoid blasts. During the regeneration of the thymus, the thymic stromal architecture is restored before the expression of cell surface-associated reticular MHC staining patterns. The observed sequential changes in the thymic microenvironment are related to the lymphoid repopulation of the thymus.

Animals↗
PubMed1984

Immunohistology of thymic nurse cells.

The demonstration of thymic nurse cells (TNC), complexes between stromal cells and thymocytes, in cell suspensions of murine thymuses, prompted us to investigate (1) the relationship of TNC to other thymic stromal cell types defined in situ, and (2) the maturation stage of the enclosed thymocytes. To this purpose we incubated frozen sections of TNC suspensions with various monoclonal antisera directed to T cells and stromal cell types, using immunohistology. This approach enabled us to study antigen expression on the "nursing" cell itself and to analyze the phenotype of the enclosed lymphocytes in cross sections of TNC. The results show that lymphocytes enveloped by TNC express high levels of Thy-1, moderate levels of T200, and variable amounts of Lyt-1. Due to enzymatic degradation Lyt-2 expression could not be studied. The enveloped cells also bear PNA receptors, but no detectable I-A/E antigens. Expression of H-2K antigens on enclosed thymocytes varied from weak to absent. The "nursing" cells react with ER-TR4, a monoclonal antibody which detects cortical epithelial-reticular cells. In addition TNC express I-A/E and H-2K antigens. In contrast, TNC do not react with ER-TR 5 and 7, monoclonal antibodies, which detect medullary epithelial cells and reticular fibroblasts, respectively. TNC do not express the macrophage antigens Mac-1 and Mac-2. We conclude that TNC in vitro represent the in vivo association of epithelial-reticular cells with cortical thymocytes. However, the enclosed thymocytes do not constitute a phenotypically distinct subset of subcapsular or outer cortical cells.

Animals↗
PubMed1983

A Rauscher-virus-induced T-lymphocyte cell line. Induction of differentiation under influence of dimethylsulfoxide and phorbolesters.

DBA/2 mice which are neonatally infected with Rauscher helper virus (R-MuLV) develop predominantly lymphatic leukemias. From one of these lymphatic leukemias we established a permanent cell line which we named RLD (Rauscher Lymphoid DBA/2). Phenotyping of this cell line with a panel of monoclonal antibodies directed to cell-surface determinants shows that RLD cells have T-cell characteristics: they bind monoclonal antibodies directed to the antigens Thy-1, T-200 and Lyt-1; they do not react with anti-Lyt-2 antibodies, nor do they react with antibodies directed to determinants on B cells or myelomonocytic cells. RLD cells show a high activity of the nuclear enzyme terminal deoxyribonucleotidyl transferase (TdT). RLD cells are able to differentiate after in vitro stimulation with 1% DMSO or with 30 nM tetradecanoylphorbol-1.3-acetate (TPA). This differentiation process is reflected by (1) changes in the 2D gel electrophoresis pattern of metabolically labelled proteins, (2) a decrease in TdT activity and (3) changes in the expression of cell-surface markers. Flow cytometric analysis of stimulated RLD cells shows a strong increase in the Lyt-1 expression. Together these data indicate that RLD cells are immature T lymphocytes which upon appropriate stimulation differentiate along the line of T helper cells.

Animals↗
PubMed1980

Migration of B lymphocytes in lymphoid organs of lethally irradiated, thymocyte-reconstituted mice.

The migration of radiolabeled intravenously injected B lymphocytes through thymus-dependent areas was studied in lymphoid organs of mice with experimentally defined T cell domains (B cell-deprived mice or "T" mice). In the spleen, B cells were found to enter the peri-arteriolar lymphoid sheath (PALS) by two routes: (i) via the marginal zone, and (ii) via reticulum sheaths surrounding terminal arterioles. B cells migrated through the peripheral and central PALS and initiated the formation of primary follicles in the peripheral PALS 6 h after injection. Distinct primary follicles were noted at 18 h after injection of the labelled B cells. After 24 h small numbers of labelled cells were also noted in the efferent lymphatic vessels of the spleen. The reconstitution of B cell compartments in the mesenteric lymph node was delayed compared to the spleen. B cells entered the nodal stroma across the wall of high endothelial venules in the paracortex and by 6 h were found scattered throughout the paracortex. Isolated clusters of a few labeled cells were noted in the outer cortex at 18 h after cell transfer. Defined primary nodules were seen only 24 h after reconstitution. A minority of labeled cells was found at 24 h in the cortico-medullary junctions and in medullary cords. The present study shows that B lymphocytes traverse T cell domains on their way to their own specific B cell compartments. The immunological significance of this particular migration route is discussed in view of data on the cellular cooperation of B cells, T cells and macrophages during the humoral immune response.

Animals↗
PubMed1979

Expression of MHC antigens by mouse thymic dendritic cells.

Thymic epithelial cells express MHC antigens in several different patterns. I-A is present throughout the thymic cortex on dendritic cells. The remainder of the I region and H-2K/D are expressed on dendritic cells apparently only variably in the cortex (at least in some haplotypes). All MHC antigens tested are present in the medulla on epithelial cells; expression on medullary lymphocytes cannot be evaluated. Monoclonal anti-MHC antibodies confirm these results. The significance of these findings to T cell maturation is discussed.

Animals↗
PubMed1978

B lymphocyte differentiation in lethally irradiated and reconstituted mice. A histological study using immunofluorescent detection of B lymphocytes.

The recovery of the B lymphocyte compartments was investigated in lethally irradiated mice reconstituted with fetal liver cells. This was done by means of immunofluorescence on frozen sections of spleen, lymph nodes and Peyer's patches. The first B lymphocyte recovery in the spleen was observed on day 8, a few days earlier than in lymph nodes and Peyer's patches (day 13). These early B cells in the spleen were found in the central part of the periarteriolar lymphatic sheath (PALS). Later on, while increasing in number, the B cells formed growing follicles at the periphery of the PALS. Subsequently, brightly fluorescent B cells appeared in the marginal zone, which surrounded the follicles. Another two weeks later, around day 30, also germinal center formation was observed in the follicles of the spleen. B cell development in lymph nodes and Peyer's patches started somewhat later than in the spleen, but once started, the recovery of the different compartments was completed very fast. Germinal center reactions were found in lymph nodes and Peyer's patches already on day 25, and thus earlier than in the spleen, but later than the first occurrence of the strongly fluorescent cells in the marginal zone. Apparently, germinalcenter formation is not essential for the recovery of the population of brightly fluorescent B cells in the marginal zone after irradiation and reconstitution.

Animals↗