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Biomedical subjects

P Engel

Publications and source records attributed to P Engel.

At least 37 records · Page 2Linked to original sources
PubMed2000

Production and characterization of monoclonal antibodies against conserved epitopes of P-selectin (CD62P).

P-selectin (CD62P) is an adhesion molecule expressed on the activated endothelium and activated platelets that is involved in the initial attachment of leukocytes to inflamed vascular endothelium. Blocking monoclonal antibodies (mAbs) and P-selectin-deficient mice have shown that P-selectin is a potential target in anti-inflammatory therapy. Most mAbs against P-selectin do not bind to conserved epitopes, including the ligand-binding region, since P-selectin from mammalian species shares high amino acid sequence homology. The aim of this study was to generate a novel panel of anti-P-selectin mAbs against the conserved epitopes present in several animal species. To produce these mAbs, P-selectin-deficient mice were immunized with a pre-B-cell line transfected with human P-selectin cDNA. Twelve mouse mAbs that recognize human P-selectin were obtained. Individual mAbs that bound to human, rat, mouse, rabbit and pig activated platelets were characterized by flow-cytometry, immunohistochemistry, adhesion assays and immunoprecipitation. Four of these mAbs (P-sel.KO.2.3, P-sel.KO.2.4, P-sel.KO.2.7 and P-sel.KO.2.12) cross-reacted with human, rat and mouse P-selectin. Another three mAbs (P-sel.KO.2.2, P-sel.KO.2.11 and P-sel.KO.2.12) blocked the attachment of HL60 cells to P-selectin-transfected COS cells, demonstrating that these mAbs inhibit P-selectin-mediated adhesion. MAb cross-blocking experiments showed that these three mAbs bind to very close and overlapping epitopes. An ELISA assay using mAbs P-sel.KO.2.3 and P-sel.KO.2.12 was designed to measure soluble rat, mouse and human P-selectin. These anti-P-selectin mAbs are unique since they recognize common epitopes conserved during mammalian evolution and they may be useful for studying P-selectin function in inflammatory models in various species.

Animals↗
PubMed2000

Increased serum levels of soluble L-selectin (CD62L) in patients with active systemic lupus erythematosus (SLE).

The adhesion molecule L-selectin (CD62L) mediates lymphocyte recirculation and leucocyte rolling on vascular endothelium at sites of inflammation. Serum levels of soluble L-selectin (sL-selectin) were measured in patients with SLE in order to relate these levels to clinical activity and immunological parameters. An ELISA was used to detect the soluble form of human L-selectin (CD62L) in 42 patients with SLE and in 33 healthy individuals. The mean +/- s.e.m. values of sL-selectin were 1285 +/- 121 ng/ml for patients with SLE and 986 +/- 180 ng/ml for healthy blood donors, but there was no significant difference. When patients with active SLE were analysed, higher levels of circulating sL-selectin were found when compared with patients without activity (1497 +/- 167 ng/ml versus 941 +/- 150 ng/ml; P = 0.028). We found a significant correlation between the levels of sL-selectin and of dsDNA antibodies (r = 0.36, P = 0. 044) and between levels of sL-selectin and SLE Disease Activity Index (SLEDAI) score (r = 0.42, P = 0.003). Patients with active SLE studied cross-sectionally showed significant elevations of sL-selectin (CD62L) compared with controls. Thus, the levels of this soluble adhesion molecule correlated with active disease and levels of anti-dsDNA antibodies.

Adolescent↗
PubMed2000

The contraction types of parallelohedra in E5

Using the process of zone contraction and its inverse, zone extension, the 179372 contraction types of parallelohedra in E(5) were derived from the 84 combinatorial types of relatively or totally zone-contracted parallelohedra.

Journal Article↗
PubMed2000

Circulating concentrations of soluble L-selectin (CD62L) in patients with primary Sjögren's syndrome.

OBJECTIVE: Serum concentrations of soluble (s) L-selectin (CD62L) were measured in patients with primary Sjögren's syndrome (SS) to relate these concentrations to clinical and immunological features of SS. METHODS: The study included 40 consecutive patients (38 women and two men) with a mean age of 61 years (range 24-78) who fulfilled four or more of the preliminary diagnostic criteria for SS proposed by the European Community Study Group in 1993, and 33 healthy blood donors from the hospital blood bank. A sandwich enzyme linked immunosorbent assay (ELISA) was used to detect the soluble form of human sL-selectin (CD62L). RESULTS: The mean (SEM) values of sL-selectin (CD62L) were 861 (66) microg/ml for patients with SS and 986 (180) microg/ml for healthy blood donors, but there was no significant difference. In patients with primary SS, serum sL-selectin (CD62L) concentrations were significantly higher in patients with Raynaud's phenomenon (1275 (112) microg/ml versus 789 (69) microg/ml, p=0.007), autoimmune thyroiditis (1162 (113) microg/ml versus 787 (69) microg/ml, p=0.02) and rheumatoid factor (993 (95) microg/ml versus 684 (70) microg/ml, p=0.01) when compared with patients without these features. CONCLUSION: The presence of Raynaud's phenomenon, autoimmune thyroiditis and rheumatoid factor is associated with higher concentrations of circulating sL-selectin (CD62L) in the sera of patients with primary SS.

Adult↗
PubMed1999

Guanylyl cyclases with the topology of mammalian adenylyl cyclases and an N-terminal P-type ATPase-like domain in Paramecium, Tetrahymena and Plasmodium.

We cloned a guanylyl cyclase of 280 kDa from the ciliate Paramecium which has an N-terminus similar to that of a P-type ATPase and a C-terminus with a topology identical to mammalian adenylyl cyclases. Respective signature sequence motifs are conserved in both domains. The cytosolic catalytic C1a and C2a segments of the cyclase are inverted. Genes coding for topologically identical proteins with substantial sequence similarities have been cloned from Tetrahymena and were detected in sequences from Plasmodium deposited by the Malaria Genome Project. After 99 point mutations to convert the Paramecium TAA/TAG-Gln triplets to CAA/CAG, together with partial gene synthesis, the gene from Paramecium was heterologously expressed. In Sf9 cells, the holoenzyme is proteolytically processed into the two domains. Immunocytochemistry demonstrates expression of the protein in Paramecium and localizes it to cell surface membranes. The data provide a novel structural link between class III adenylyl and guanylyl cyclases and imply that the protozoan guanylyl cyclases evolved from an ancestral adenylyl cyclase independently of the mammalian guanylyl cyclase isoforms. Further, signal transmission in Ciliophora (Paramecium, Tetrahymena) and in the most important endoparasitic phylum Apicomplexa (Plasmodium) is, quite unexpectedly, closely related.

Amino Acid Sequence↗
PubMed1999

Molecular cloning, characterization, and chromosomal localization of the mouse homologue of CD84, a member of the CD2 family of cell surface molecules.

CD84 is a member of the immunoglobulin gene superfamily (IgSF) with two Ig-like domains expressed primarily on B lymphocytes and macrophages. Here we describe the cloning of the mouse homologue of human CD84. Mouse CD84 cDNA clones were isolated from a macrophage library. The nucleotide sequence of mouse CD84 was shown to include an open reading frame encoding a putative 329 amino acid protein composed of a 21 amino acid leader peptide, two extracellular immunoglobulin (Ig)-like domains, a hydrophobic transmembrane region, and an 87 amino acid cytoplasmic domain. Mouse CD84 shares 57.3% amino acid sequence identity (88.7%, considering conservative amino acid substitutions) with the human homologue. Chromosome localization studies mapped the mouse CD84 gene to distal chromosome 1 adjacent to the gene for Ly-9, placing it close to the region where other members of the CD2 IgSF (CD48 and 2B4) have been mapped. Northern blot analysis revealed that the expression of mouse CD84 was predominantly restricted to hematopoietic tissues. Two species of mRNA of 3.6 kilobases (kb) and 1.5 kb were observed. The finding that the pattern of expression was restricted to the hematopoietic system and the conserved sequence of the mouse CD84 homologue suggests that the function of the CD84 glycoprotein may be similar in humans and mice.

Amino Acid Sequence↗
PubMed1999

Thymic tumours in Denmark. A retrospective study of 213 cases from 1970-1993.

Histological slides of 213 thymic tumours were reviewed twice and classified according to Kirchner and Müller-Hermelink into 122 thymomas (syn. organotypic thymic epithelial tumours (TET)), 58 thymic carcinomas (syn. non-organotypic TET) and 16 lymphomas. Tumour heterogeneity (i.e. features of two subtypes in one tumour) appeared in 38% of the organotypic TET. The overall diagnostic correspondence between the reviews of the 122 organotypic TET was 48%. By reducing the five diagnostic groups to three: organotypic TET benign (medullary and mixed thymomas), organotypic TET low-grade (organoid and cortical thymomas and well-differentiated thymic carcinoma (WDTC)) and non-organotypic TET (usually high-grade thymic carcinomas), and minimising the effect of tumour heterogeneity in this way, the diagnostic correspondence increased to 82%. Correlating histological type with stage, we found that 80% of medullary and 87% of mixed thymomas were stage I, that 85% of cortical and 81% of WDTC were stage II or III, and that non-organotypic TET were stage II or III (86%) or stage IV (14%), respectively. It is suggested to report on the heterogeneity of a given case of thymic epithelial tumour in the pathology reports and give the approximate percentage of each component, telling the clinician which component may determine the prognosis.

Cysts↗
PubMed1999

Mitigation of delayed-type hypersensitivity reactions by a CD44 variant isoform v3-specific antibody: blockade of leukocyte egress.

In allergic alterations of human skin the majority of infiltrated leukocytes express CD44v3, but no other CD44 variant isoform. Vessel endothelium, too, is brightly stained with a CD44v3-specific antibody. Being concerned about therapeutic intervention, it became of importance to define whether expression of CD44v3 on the endothelial cells or on the leukocytes or on both is of functional importance. As expression of CD44v3 in the mouse on activated endothelium and on subpopulations of activated CD4+ cells, B cells and monocytes was similar to the expression in the human, we answered the question in a mouse delayed-type hypersensitivity model. The effect of anti-CD44v3 was compared with the effect of anti-CD44s and anti-CD44v10, both known to suppress delayed-type hypersensitivity reactions. Anti-CD44v3 mitigated the delayed-type hypersensitivity reaction in dinitrofluorobenzene sensitized and challenged mice comparable with anti-CD44s and anti-CD44v10. The seemingly similar effects of CD44 isoform-specific antibodies, however, resulted from a distinct modulation of response. Anti-CD44s mainly suppressed T cell activation and interleukin-2 as well as interferon-gamma expression. Anti-CD44v10 inhibited the activation of monocytes in the draining lymph nodes and in the infiltrate, which led to a strong reduction in the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-12 and in edema formation. Anti-CD44v3 had only a weak effect on cytokine expression by isolated subpopulations of leukocytes, but suppressed cytokine production by helper T cells when cocultured with antigen-presenting cells, i.e., blocked an interaction between antigen-presenting cells and helper T cells. The dominating effect of anti-CD44v3, however, relied on a blockade of leukocyte extravasation. As leukocytes transferred into dinitrofluorobenzene sensitized, anti-CD44v3-treated and lethally irradiated mice did not infiltrate the sensitized skin, anti-CD44v3 most likely prevented leukocyte extravasation by blocking CD44v3 on endothelial cells.

Adult↗
PubMed1998

Expression of bcl-2 in fetal thymus, thymomas and thymic carcinomas. Association with p53 expression and review of the literature.

Bcl-2 is a proto-oncogene inhibiting apoptosis, and p53 is a tumor supressor gene which induces apoptosis. Both seem to take part in tumorigenesis. An inverse relationship between the two genes has been reported in some neoplasms, although the exact mechanism is not fully understood. We have analyzed the expression of bcl-2 and p53 in 18 fetal thymuses and 18 clinically benign and malignant thymomas: bcl-2 was expressed by most medullary lymphocytes and epithelial cells of the normal thymus; p53 was not expressed at all. Bcl-2 and p53 were co-expressed in the majority of the thymomas and the staining reaction was stronger in the clinically malignant ones. It is concluded that although co-expression of bcl-2 and p53 is of doubtful prognostic relevance, the staining pattern of bcl-2 supports the histogenetic classification system of Müller-Hermelink.

Fetus↗
PubMed1998

Leukocyte infiltration and intercellular adhesion molecule-1-mediated cell interactions in immunoglobulin A nephropathy.

BACKGROUND: Mononuclear leukocytes have a role in immunoglobulin (Ig) A nephropathy. Renal leukocyte recruitment is mediated by adhesive interactions between leukocytes and their ligands on renal cells. METHODS: We assessed interstitial and glomerular leukocytes using an avidin-biotin-peroxidase method with monoclonal antibodies (MAbs) against leukocytes (CD45), beta2-integrin (CD18), macrophages (CD14), T cells (CD3) and T-cell subsets (CD4, CD8), intercellular adhesion molecule-1 (ICAM-1) (CD54), and HLA class II antigens. We analyzed their relation with the abnormal expression of ICAM-1 on proximal tubular epithelium in sequential renal sections from 57 patients with IgA nephropathy stratified by degrees of interstitial cellular infiltration as seen by light microscopy. RESULTS: In IgA nephropathy without infiltration (n = 15) and with interstitial cellular infiltration of 1+ by light microscopy (n = 11), ICAM-1 expression on vascular endothelium was unchanged with respect to that observed in the normal kidney; the proximal tubular epithelium was negative for this stain. Moreover, in IgA nephropathy with interstitial cellular infiltration greater than or equal to 2+ by light microscopy (n = 31), ICAM-1+ stain was seen on proximal tubular epithelium. The value of ICAM-1+ tubule staining was significantly (P = .0004) higher in the biopsies with a higher degree of interstitial cellular infiltration seen by light microscopy. The tubular ICAM-1+ stain was significantly associated with the number of interstitial leukocytes identified by the MAbs tested and correlated (P < .05) with CD45+ (r = 0.59), CD14+ (r = 0.54), and CD3+ (r = 0.51) interstitial leukocytes in IgA nephropathy with interstitial cellular infiltration by light microscopy. Interstitial ICAM-1+ cells and interstitial CD18+ leukocytes were correlated (r = 0.85, P < .001). Correlation was found between the value of ICAM-1+ tubule staining and the number of CD45+ (r = 0.87, P < .01), CD14+ (0.58, P < .05), and CD8+ (r = 0.68, P < .05) glomerular leukocytes. CONCLUSIONS: Our results suggest that tubular and interstitial ICAM-1+ cells may participate in adhesive interactions with interstitial leukocytes. Epithelial tubular cells expressing ICAM-1 may be a marker of tubulointerstitial disturbance upregulated by interstitial and glomerular infiltration of macrophages and T cells in IgA nephropathy.

Cell Communication↗
PubMed1997

CD84 leukocyte antigen is a new member of the Ig superfamily.

cDNA isolated from a human B-cell line Raji library was analyzed and shown to encode the full-length cDNA sequence of a novel cell-surface glycoprotein, initially termed HLy9-beta. The predicted mature 307-amino acid protein was composed of two extracellular Ig-like domains, a hydrophobic transmembrane region, and an 83-amino acid cytoplasmic domain. The extracellular Ig-like domains presented structural and sequence homology with a group of members of the Ig superfamily that included CD2, CD48, CD58, and Ly9. Northern blot analysis showed that the expression of HLy9-beta was predominantly restricted to hematopoietic tissues. Chromosome localization studies mapped the HLy9-beta gene to chromosome 1q24, where other members of this Ig superfamily (CD48 and HumLy9) have been mapped. CD84 monoclonal antibodies (MoAbs) were shown to react with cells transfected with the cloned cDNA. These MoAbs were further used to show that CD84 is expressed as a single chain cell-surface glycoprotein of Mr 64,000 to 82,000, which was highly glycosylated. CD84 had a unique pattern of expression, being found predominantly on lymphocytes and monocytes. Thus, the glycoprotein HLy9-beta is recognized by MoAbs previously clustered as CD84 and represents a newly identified member of the Ig superfamily that may play a significant role in leukocyte activation.

Amino Acid Sequence↗
PubMed1997

Ligation of L-selectin through conserved regions within the lectin domain activates signal transduction pathways and integrin function in human, mouse, and rat leukocytes.

L-selectin is a cell surface adhesion receptor that mediates leukocyte rolling along vascular endothelium at sites of inflammation and lymphocyte attachment to endothelial cells within peripheral lymphoid tissues. Since ligation of L-selectin through its ligand recognition region may mimic physiologic ligand binding, a new panel of mAbs that engaged a conserved ligand-binding region within the lectin domains of human, mouse, and rat L-selectin were generated using L-selectin-deficient mice. Indeed, appropriate ligation of L-selectin generated transmembrane signals that resulted in immediate intercellular adhesion following cell-cell contact of lymphocytes, neutrophils, and L-selectin cDNA-transfected cells. Ab binding to only some epitopes within the lectin domain of L-selectin induced adhesion, while mAb binding to numerous other epitopes or other domains of L-selectin had no effect. PPME (yeast polyphosphomonoester core polysaccharide), a complex carbohydrate that mimics the natural L-selectin ligand, also induced potent intercellular adhesion. The induction of intercellular adhesion required cellular energy, an intact cytoskeleton, and cytoplasmic kinase activity as well as the membrane proximal and cytoplasmic domains of L-selectin. Therefore, ligation of L-selectin through specific ligand-binding epitopes identified by the mAbs generated in this study can generate transmembrane signals. Signaling through L-selectin may enhance leukocyte-endothelial cell interactions by serving as an activation/priming step during rolling, thereby promoting subsequent firm cell-cell adhesion in the presence of inflammatory mediators.

Amino Acid Sequence↗
PubMed1997

Metastasizing sarcoma of the aorta. A case report.

Sarcomas of the great vessels are rats. We report a case of a metastasizing sarcoma of the aorta. The patient was an 82-year-old male who presented with a subcutaneous tumour, which was initially classified as a malignant fibrous histiocytoma. Autopsy revealed a polypoid sarcoma of the luminal aspect of the aortic arch with metastases to several organs. By means of immunohistochemical staining, the aortic neoplasm was classified as an undifferentiated intimal sarcoma. The morphology of intimal sarcomas is very heterogeneous, and, when metastatic deposits are present, there may be considerable problems in differential diagnosis.

Aged↗
PubMed1996

Engagement of the adhesion receptor CD22 triggers a potent stimulatory signal for B cells and blocking CD22/CD22L interactions impairs T-cell proliferation.

The B-lymphocyte-restricted adhesion protein CD22 mediates sialic acid-dependent cell-cell interactions. Engagement of CD22 on B lymphocytes with a CD22 monoclonal antibody (MoAb) HB22.7 that blocks the binding of CD22 to its ligand(s) directly stimulated B-cell proliferation. In addition, the HB22.7 MoAb costimulated B-cell proliferation with either anti-IgM, interleukin-2 (IL-2), IL-4, or CD40 and triggered predominantly B-cell IgG secretion with IL-2. Even more striking levels of B-cell proliferation occurred with HB22.7 MoAb under culture conditions that enhanced B-B-cell interactions. In contrast, a nonblocking CD22 MoAb (CD22.5) poorly costimulated in similar experiments. The functional differences between the two antibodies likely result from differing abilities to trigger downstream signaling events as significant differences in CD22 tyrosine phosphorylation and the recruitment of the tyrosine kinase p53/56lyn and the tyrosine phosphatase SH-PTP1C were found. Besides their role in B-cell stimulation, CD22/CD22L interactions may also assist in regulating T-cell proliferation because inhibition of CD22-CD22L engagement with the HB22.7 MoAb impaired T-cell proliferation in a costimulatory assay. Thus, CD22/CD22L interactions result in stimulatory signals for both B and T lymphocytes.

Amino Acid Sequence↗
PubMed1996

Involvement of p72syk kinase, p53/56lyn kinase and phosphatidyl inositol-3 kinase in signal transduction via the human B lymphocyte antigen CD22.

CD22 is a B lymphocyte-specific membrane protein that functions as an adhesion molecule via its interactions with a subset of alpha 2-6-linked sialic acid-containing glycoproteins. Engagement of CD22 with a monoclonal antibody (HB22.23) that blocks the binding of CD22 to its ligands results in rapid CD22 tyrosine phosphorylation and in increased association of CD22 with p53/56lyn kinase, p85 phosphatidyl inositol-3 kinase, and p72syk kinase. Synthetic peptides that span various regions of the intracellular portion of CD22 were used to map potential kinase binding sites. All three kinases associated with a tyrosine-phosphorylated peptide that spans tyrosine amino acid residues 822 and 842, implicating this as an important region in mediating CD22 signal transduction. In addition, purified p56lyn directly bound to the same peptide. Engagement of CD22 with HB22.23 was sufficient to stimulate normal B cell proliferation. This study further substantiates the importance of CD22 as a B lymphocyte signaling molecule and begins to unravel the mechanisms by which CD22 cross-linking can alter B cell function.

Amino Acid Sequence↗