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A van Leeuwen

Publications and source records attributed to A van Leeuwen.

At least 19 recordsLinked to original sources
PubMed1997

Monoclonal antibodies against the human mannose receptor as a specific marker in flow cytometry and immunohistochemistry for macrophages.

Recently we developed mouse monoclonal antibodies (mAb) against the isolated human 175-kDa mannose receptor. In the present study we tested whether these mAb are suitable for the detection of the mannose receptor on cultured macrophages using flow cytometry and on cells in human tissues using immunohistochemistry. Human monocytes did not react with the mAb in flow cytometry. Mannose receptor expression became detectable on monocytes cultured for 3 days (macrophages), and was maximal from 4 days onward. The mannose receptor was up-regulated on dexamethasone-treated (immunosuppressed) macrophages, and down-regulated on lipopolysaccharide-treated (activated) macrophages. Immunohistochemically the staining pattern of our mAb was compared with the marker of monocytes/macrophages KP1. In a bone marrow smear, only macrophages were stained with our mAb, whereas all myeloid cells were stained with KP1. In the thymus and lymph node, mannose receptor-positive branched cells (macrophages and dendritic cells) were detected in connective tissue, thymus cortex (not medulla), and in the T cell area (not the B cell area) of lymph nodes, whereas KP1 stained branched cells in all areas. It was concluded that the mAb are useful tools in flow cytometry and immunohistochemistry for the specific detection of cells expressing mannose receptor.

Antibodies, Monoclonal↗
PubMed1994

Bone Marrow Donors Worldwide: a successful exercise in international cooperation.

Bone marrow transplantation using unrelated donors has become a clinical reality but a large number of challenges remain. One of the most important and a crucial one is locating a suitable donor. To cope with this very large registries have been formed but each of these lacks donors with phenotypes which occur in other registries. To facilitate the search process a collation system designated Bone Marrow Donors Worldwide (BMDW) was started. Several times a year it collects the phenotypes of all donors from all participating registries on a worldwide basis. The data are sorted by phenotype number of the broad antigens; the splits are specified immediately after the broad phenotypes. Here the experience with the first 11 editions is summarized. Although there is a steady increase in the numbers of donors and phenotypes included in BMDW, < 1% of the theoretically possible HLA-A, -B, -DR split phenotypes are so far represented. Furthermore, 70% of these phenotypes are unique, i.e. they occur in one donor only. As a result 30% of the donors have a phenotype which occurs in one registry only. Of 49 Europdonor donors who donated bone marrow, 8 (16%) had a phenotype which did not occur in any of the other registries. Because BMDW indicates in which registry a potential donor can be located, it can reduce search time by 75%. We conclude that the use of BMDW is the fastest and most cost-effective way to locate donors with rare phenotypes, whether or not they are of Caucasoid origin.

Bone Marrow Transplantation↗
PubMed1994

The role of different histocompatibility testing methods for selection of related and unrelated bone marrow donors.

Bone marrow transplantation has become the treatment of choice for many hematological malignancies. Approximately 30% of the patients lack an HLA-identical sibling donor, for them alternative donors have to be found. The chances of finding an unrelated donor can be estimated by consulting the Bone Marrow Donors Worldwide file and grouping the patients according to whether they have frequent or rare haplotypes. If the HLA-ABDR split antigens are taken into account, for less than 25% of the patients identical donors can be identified. In order to select the best matched donor for a patient, sensitive HLA typing techniques should be employed including DNA typing techniques, but for optimal selection of a suitable donor one should not only study genetics but also determine the immunological repertoire recognizing the histocompatibility differences between donor and recipient. Several promising cellular techniques such as the HTLp and CTLp test have recently become available and should also be used to select the best donor.

Bone Marrow Transplantation↗
PubMed1993

Laboratory procedures used to select an unrelated HLA matched bone marrow donor.

Selecting an HLA matched unrelated bone marrow donor is a labour-intensive step-by-step procedure, with highly specialized techniques. To be successful immunohematologists and clinicians have to work closely together. Because so much is still unknown lymphocytes and serum of patient and donor should be stored to enable future analyses.

Bone Marrow Transplantation↗
PubMed1992

Enzymatic preparation of 1,6-anhydro-muropeptides by immobilized murein hydrolases from Escherichia coli fused to staphylococcal protein A.

In order to produce biologically active 1,6-anhydro-muropeptides in large amounts by enzymatic degradation of isolated bacterial murein polymer highly specific periplasmic murein-metabolizing enzymes from Escherichia coli are made available. The genes slt, dacB, and mepA, encoding the soluble lytic transglycosylase (Slt), the penicillin-sensitive DD-endopeptidase (PBP4), and the penicillin-insensitive murein endopeptidase A (MepA), were independently fused to the N-terminal encoding sequence of staphylococcal protein A (SpA) under control of the temperature-inducible phage lambda pR promoter. The SpA fusion proteins were stably over-produced at high levels in E. coli upon temperature induction at 42 degrees C and account for 3% (5 mg SpASlt/l culture), 3% (5 mg SpAPBP4/l culture), and 0.3% (0.5 mg SpAMepA/l culture) of total protein. The SpA fusion proteins, immobilized on IgG Sepharose, are proteolytically sensitive, in vitro, resulting in complete degradation of the SpA portion of the fusion proteins and release of the murein hydrolases in intact and enzymatically active form into the supernatant. Proteolytic degradation could be prevented by p-hydroxymercuribenzoic acid (PHMB) or ethylenediaminetetraacetate (EDTA) suggesting the involvement of the periplasmic protease Pi from E. coli. The immobilized fusion proteins were enzymatically active and could be used for the batch production of biologically active 1,6-anhydro-muropeptides, which were successively separated on HPLC. Isolated murein polymer was degraded quantitatively to monomeric 1,6-anhydro-muropeptides when immunoglobulin G (IgG)-SpASlt was used in combination with IgG-SpAMepA. A combination of IgG-SpASlt with IgG-SpAPBP4 left the 1,6-anhydro-dimers and oligomers being cross-linked via an LD-peptide bond (m-DAP-m-DAP) uncleaved.

Amino Acid Sequence↗
PubMed1990

N-myc expression switched off and class I human leukocyte antigen expression switched on after somatic cell fusion of neuroblastoma cells.

Neuroblastomas often show amplification and high expression of the N-myc oncogene. N-myc expression could be explained as a consequence of gene amplification, but an alternative possibility is that expression primarily results from the inactivation or loss of some factor that normally represses the N-myc gene. To test this idea, we fused N-myc-overexpressing neuroblastoma cell lines with lines that do not express N-myc. In the resulting hybrids, N-myc expression turned out to be switched off, although amplified N-myc copies were still present. This suggests that N-myc overexpression in neuroblastomas results, at least in part, from the inactivation of a suppressor gene that is present in normal cells. In rat neuroblastomas, it has been found that N-myc can switch off class I major histocompatibility complex (MHC) expression. Therefore, we analyzed in our hybrid cells whether suppression of N-myc results in reexpression of human class I MHC genes. Because this was found to be the case, the picture emerges of a hierarchic pathway that connects a putative tumor-suppressor gene with the expression of N-myc and consequently of class I MHC, thus affecting the potential immunogenic properties of neuroblastomas.

Animals↗
PubMed1990

Trial and error in producing ankylosing-spondylitis-selective antisera according to Andrew Geczy.

Geczy found that rabbit sera raised against Klebsiella strain K43 cross-reacted with the cells from HLA-B27 positive patients with ankylosing spondylitis (AS). Other laboratories failed to reproduce these results. After a series of unsuccessful attempts, however, we managed to prepare one selective antiserum, using E. coli, isolated from a Dutch Bechterew patient, in offspring of rabbits Geczy sent us. Ever since we obtained irreproducible results only. This paper reports about the many attempts we have made to produce a discriminating antiserum for use in a combined vital stain and dye-exclusion assay.

Animals↗
PubMed1989

Suppression of class I human histocompatibility leukocyte antigen by c-myc is locus specific.

The c-myc oncogene downregulates class I HLA expression in human melanoma. The major class I HLA antigens are encoded by three loci, A, B, and C, and we investigated whether these loci are suppressed equally by c-myc. In three melanoma cell lines with high c-myc expression, we analyzed mRNA, protein, and cell surface expression of the class I HLA antigens. Whereas the HLA-B locus expression was found to be strongly reduced, the HLA-A locus was expressed normally. Analysis of c-myc-transfected clones of two melanoma cell lines confirmed that c-myc preferentially suppresses the class I HLA-B locus. Immunohistochemical analysis of fresh melanoma lesions also showed that in the tumors the HLA-A loci are expressed normally, while on the majority of tumor cells no HLA-B antigen expression was found. This downregulation may have consequences for the recognition of malignant cells by tumor-infiltrating lymphocytes. Our results predict that HLA-B-restricted cytotoxic T cells will be unable to kill high c-myc-expressing melanoma cells.

Alleles↗
PubMed1989

In vivo effects of combination treatment with recombinant interferon-gamma and -alpha in metastatic melanoma.

The toxicity and therapeutic efficacy of the combination of recombinant interferon gamma (rIFN-gamma) and alpha (rIFN-alpha) was investigated in 15 patients with metastatic melanoma. Patients were treated with an escalating dose of rIFN-gamma and a fixed dose of rIFN-alpha administered s.c. 3 times a week. The maximum dose was well tolerated. The median survival time of the patients was 7 months; no clinical remissions were observed. In the majority of cases, expression of HLA class-I and -II antigens on the patients' peripheral blood lymphocytes and monocytes increased markedly during treatment. An increase in HLA-DR expression of peripheral blood T lymphocytes was correlated with a longer survival time. This suggests that activation of T lymphocytes may have a favourable influence on the course of metastatic disease. The in vitro anti-proliferative activity of IFNs on melanoma cell lines isolated from melanoma metastases during treatment of 3 patients was determined. In contrast to the lack of in vivo anti-tumour effect in patients, both rIFN-gamma and rIFN-alpha inhibited DNA synthesis of these melanoma cell lines in vitro, combined IFNs acting synergistically. Anti-proliferative activity observed in vitro occurred at IFN concentrations below the peak serum levels achieved in vivo.

Cell Division↗
PubMed1989

Hyperimmunized patients do not need to wait for an HLA identical donor.

Hyperimmunized patients tend to accumulate on renal transplant waiting lists because their high level of sensitization leads to positive crossmatches with almost all potential organ donors. The origins of sensitization and the different efforts made to find cross-match negative donors for these patients are discussed. Special emphasis is given to a local strategy based on the determination of HLA-A and -B mismatches, against which the patient did not form allo-antibodies, the so-called acceptable mismatches. Kidney donor selection is based on compatibility with the patient's own HLA-antigens in combination with the acceptable HLA-A and -B antigens, and can be operated from a central organ-sharing office. The acceptable HLA mismatches are often identical with or include the non-inherited HLA class I antigens of the mother (non-inherited maternal antigens: NIMA).

Female↗
PubMed1988

Rabbit antisera to enterobacteriaceae isolated from HLA-B27 positive patients with ankylosing spondylitis (AS) are lytic for the mononuclear cells of AS patients.

Vaccines prepared from Gram-negative bacteria isolated from the stools of HLA-B27 positive AS patients were used to immunize rabbits. Three of the sera obtained were lytic in vitro for the mononuclear cells of HLA-B27 positive AS patients. One of these sera discriminated between AS patients and healthy HLA-B27 positive individuals. Cytolysis was determined in an automated, non-radioactive assay based on the release of carboxyfluorescein diacetate and the incorporation of propidium iodide.

Animals↗