Biomedical subjects
R Schwartz-Albiez
Publications and source records attributed to R Schwartz-Albiez.
CD antigens 2001.
The most recent Human Leucocyte Differentiation Antigen Workshop ("HLDA7") took place in 2000 in Harrogate, UK and the proceedings are about to be published (Leucocyte Typing VII). New Sections were introduced in this Workship (Dendritic cells, Stem/progenitor cells, Erythroid cells and Carbohydrate Structures) and monoclonal antibodies were selected for which at least some molecular data were already available (to avoid "blind" screening of reagents against known specificities). A total of more than 80 new CD specificities were established (previously the average was less than 30 new CD specificities per Workshop) and these are listed in this article. There is already evidence for the existence of many new leucocyte surface molecules for study at the next HLDA Workshop (in Adelaide in 2004), and we have listed in this article a number of such potential CD candidates (identified following the production of monoclonal antibodies or via gene cloning). There are also today an increasing number of lineage- and/or stage-restricted leucocyte-associated molecules localised within the cell cytoplasm (or nucleus): they will certainly prove of intense in the future for many laboratories studying human haematopoietic cells (regardless of whether a new "intracellular CD" categorisation scheme is devised for such molecules).
CD antigens 2001.
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The fucosylated histo-blood group antigens H type 2 (blood group O, CD173) and Lewis Y (CD174) are expressed on CD34+ hematopoietic progenitors but absent on mature lymphocytes.
The expression of LeY, H2, H3, and H4 on a broad variety of human leukemia cell lines and native lymphocytes as well as on CD34+ hematopoietic progenitor cells was examined by flow cytometry and immunocytochemistry. CD34+ leukemia cell lines (KG1, KG1a, and TF1) and native CD34+ hematopoietic progenitor cells expressed H2 (CD173) and LeY (CD174). In contrast, CD34(-) cell lines (HL-60, U937, JOK-1, Raji, Molt-3, Jurkat, and CEM-C7) and mature lymphocytes from peripheral blood and tonsils lacked CD173 and CD174. All cell lines and native lymphocytes as well as CD34+ precursor cells were negative for H3 and H4. Immunoprecipitation and consecutive Western blotting revealed a 170-kDa glycoprotein as the carrier molecule for the CD173 and CD174 oligosaccharide sequences on CD34+ hematopoietic precursors. The key enzyme for generating CD173 is the beta-D-galactoside 2-alpha-L-fucosyltransferase (FUT1). As shown by RT-PCR, FUT1 was expressed in immature hematopoietic cells but absent in mature lymphocytes, which indicates that expression of CD173 within the hematopoietic system is regulated at the transcriptional level by FUT1. Due to their exclusive presence on CD34+ hematopoietic progenitor cells, CD173 and CD174 represent novel markers of early hematopoiesis. The expression of the fucosylated histo-blood group antigens CD173 and CD174 in CD34+ hematopoietic progenitor cells and down-regulation of FUT1 in mature lymphocytes may be important factors influencing the homing process of hematopoietic stem cells to the bone marrow.
CD antigens 2001: aims and results of HLDA Workshops.
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CD antigens 2001.
This paper reviews the Seventh Human Leucocyte Differentiation Antigen (HLDA7) workshop. Due to the limitations of "blind" antibody screening, which had been evident at the previous meeting in 1996, participants at HLDA7 adopted a more selective approach to the choice of antibodies by identifying new CD specificities. This resulted in the addition of more than 80 new CD specificities. Plans for the eighth and subsequent workshops are also previewed.
Polarization and interaction of adhesion molecules P-selectin glycoprotein ligand 1 and intercellular adhesion molecule 3 with moesin and ezrin in myeloid cells.
In response to the chemoattractants interleukin 8, C5a, N-formyl-methionyl-leucyl-phenylalanine, and interleukin 15, adhesion molecules P-selectin glycoprotein ligand 1 (PSGL-1), intercellular adhesion molecule 3 (ICAM-3), CD43, and CD44 are redistributed to a newly formed uropod in human neutrophils. The adhesion molecules PSGL-1 and ICAM-3 were found to colocalize with the cytoskeletal protein moesin in the uropod of stimulated neutrophils. Interaction of PSGL-1 with moesin was shown in HL-60 cell lysates by isolating a complex with glutathione S-transferase fusions of the cytoplasmic domain of PSGL-1. Bands of 78- and 81-kd were identified as moesin and ezrin by Western blot analysis. ICAM-3 and moesin also coeluted from neutrophil lysates with an anti-ICAM-3 immunoaffinity assay. Direct interaction of the cytoplasmic domains of ICAM-3 and PSGL-1 with the amino-terminal domain of recombinant moesin was demonstrated by protein-protein binding assays. These results suggest that the redistribution of PSGL-1 and its association with intracellular molecules, including the ezrin-radixin-moesin actin-binding proteins, regulate functions mediated by PSGL-1 in leukocytes stimulated by chemoattractants.
UDP-GlcNAc 2-epimerase: a regulator of cell surface sialylation.
Modification of cell surface molecules with sialic acid is crucial for their function in many biological processes, including cell adhesion and signal transduction. Uridine diphosphate-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase) is an enzyme that catalyzes an early, rate-limiting step in the sialic acid biosynthetic pathway. UDP-GlcNAc 2-epimerase was found to be a major determinant of cell surface sialylation in human hematopoietic cell lines and a critical regulator of the function of specific cell surface adhesion molecules.
Age-dependent altered proportions in subpopulations of tonsillar lymphocytes.
Age-related changes in functional subsets of lymphocytes may influence the potential to build up immune responses. In particular, the capacity of tonsillar lymphocytes to counter infections may be altered during ageing. In order to address this question we investigated the proportional distribution of several subsets of tonsillar T and B cells with regard to ageing. Tonsils were derived from 119 patients between 2 and 65 years of age. Lymphocyte subsets were monitored by three-colour fluorescence of relevant CD markers in flow cytometry. As a general tendency the percentage of CD3+ T cells steadily increased whereas that of CD19+ B cells decreased at the same time. No significant differences were observed between lymphocytes of patients with and without inflammatory history of the tonsils. The percentage of CD8+ T cells declined whereas that of CD4+ T cells increased during the same time span. CD45RA+ T cells increased during the first two decades of life and gradually decreased thereafter. In contrast, CD45RO+ T cells showed an opposite trend. No differences were seen in the population of CD3-/CD56+ natural killer (NK) cells. The mature B cell marker CD40 showed no significant changes during ageing. However, CD38+ B cells, representing B cells of late maturation stages, dramatically declined up to the age of 65. In a similar manner the CD5+ subpopulation of B cells decreased during ageing. Substantial changes in major tonsillar T and B cell populations as shown in this study may have an impact on the ageing process of the immune system.
Differential expression of alpha2-6 sialylated polylactosamine structures by human B and T cells.
We found that human peripheral B and T cells differed in the surface expression of alpha2-6 sialylated type 2 chain glycans. In contrast to B cells, T cells expressed only sialoglycans with repeated N-acetyllactosamine (Galss1-4GlcNAc) disaccharides. This finding was based on the specificity of the monoclonal antibodies HB6, HB9 (CD24), HD66 (CDw76), FB21, and CRIS4 (CDw76) with the alpha2-6 sialylated model gangliosides IV6NeuAcnLc4Cer (2-6 SPG), VI6NeuAcnLc6Cer (2-6 SnHC), VIII6NeuAcnLc8Cer (2-6 SnOC), and X6NeuAcnLc10Cer (2-6 SnDC). We found that, in addition to their common requirement of an alpha2-6 bound terminal sialic acid for binding, the antibodies displayed preferences for the length of the carbohydrate backbones. Some of them bound mainly to 2-6 SPG with one N-acetyllactosamine (LacNAc) unit (HB9, HD66); others preferentially to 2-6 SnHC and 2-6 SnOC, with two and three LacNAc units, respectively (HB6 and FB21); and one of them exclusively to very polar alpha2-6 sialylated type 2 chain antigens (CRIS4) such as to 2-6 SnOC and even more polar gangliosides with three and more LacNAc units. These specificities could be correlated with the cellular binding of the antibodies as follows: whereas all antibodies bound to human CD 19 positive peripheral B cells, their reactivity with CD3 positive T cells was either nearly lacking (HD66, HB9), intermediate (about 65%: HB6, FB21) or strongly positive (CRIS4, 95%). Thus, the binding of the antibodies to 2-6 sialylated glycans with multiple lactosamine units appeared to determine their binding to T-cells.
Differential sialylation of cell surface glycoconjugates in a human B lymphoma cell line regulates susceptibility for CD95 (APO-1/Fas)-mediated apoptosis and for infection by a lymphotropic virus.
Sialic acid, as a terminal saccharide residue on cell surface glycoconjugates, plays an important role in a variety of biological processes. In this study, we investigated subclones of the human B lymphoma cell line BJA-B for differences in the glycosylation of cell surface glycoconjugates, and studied the functional implications of such differences. With respect to the expression level of most of the tested B cell-associated antigens, as well as the presence of penultimate saccharide moieties on oligosaccharide chains, subclones were phenotypically indistinguishable. Marked differences among subclones, however, were found in the overall level of glycoconjugate sialylation, involving both alpha-2,6 and alpha-2,3-linked sialic acid residues. Accordingly, subclones were classified as highly- (group I) or hyposialylated (group II). The function of two sialic acid-dependent receptor-mediated processes is correlated with the sialylation status of BJA-B subclones. Susceptibility to and binding of the B lymphotropic papovavirus (LPV) was dependent on a high sialylation status of host cells, suggesting that differential sialylation in BJA-B cells can modulate LPV infection via its alpha-2,6-sialylated glycoprotein receptor. CD95-mediated apoptosis, induced by either the human CD95 ligand or a cytotoxic anti-CD95 monoclonal antibody, was drastically enhanced in hyposialylated group II cells. An increase in endogenous sialylation may be one antiapoptotic mechanism that converts tumor cells to a more malignant phenotype. To our knowledge, this is the first report demonstrating that differential sialylation in a clonal cell line may regulate the function of virus and signal-transducing receptors.
Identification of an alpha2,6-sialyltransferase induced early after lymphocyte activation.
We have used mRNA differential display PCR to search for genes induced in activated T cells and we identified a gene encoding an alpha2,6-sialyltransferase (ST6GalNAc IV) that is rapidly induced in lymphocytes after antigen or mitogen stimulation. The 3.6 kb full-length cDNA clone (MK45) obtained contained a single open reading frame encoding a 302 amino acid protein and a 2.5 kb 3' untranslated region. MK45 expression in in vivo-activated CD8 T cells reached the highest level 4 h after antigen triggering and then declined rapidly to nearly base levels within 45 h. Northern blot analysis further revealed that MK45 expression was also induced in LPS-activated B cells and antigen-triggered CD4 T cells in vitro. MK45 expression was low or undetectable in most other mouse tissues examined, when compared to activated lymphocytes. Importantly, the mRNA expression level of other sialyltransferases remained largely unchanged during the early stage of lymphocyte activation. Finally, increased ecto-sialyltransferase activity and an altered sialylation pattern were demonstrated on the cell surface of early activated CD8 T cells. Our report identifies a candidate sialyltransferase gene that is involved in the early alteration of the sialylation pattern of cell surface molecules in activated lymphocytes.
CD43 interacts with moesin and ezrin and regulates its redistribution to the uropods of T lymphocytes at the cell-cell contacts.
Chemokines as well as the signaling through the adhesion molecules intercellular adhesion molecule (ICAM)-3 and CD43 are able to induce in T lymphocytes their switching from a spherical to a polarized motile morphology, with the formation of a uropod at the rear of the cell. We investigated here the role of CD43 in the regulation of T-cell polarity, CD43-cytoskeletal interactions, and lymphocyte aggregation. Pro-activatory anti-CD43 monoclonal antibody (MoAb) induced polarization of T lymphocytes with redistribution of CD43 to the uropod and the CCR2 chemokine receptor to the leading edge of the cell. Immunofluorescence analysis showed that all three ezrin-radixin-moesin (ERM) actin-binding proteins localized in the uropod of both human T lymphoblasts stimulated with anti-CD43 MoAb and tumor-infiltrating T lymphocytes. Radixin localized at the uropod neck, whereas ezrin and moesin colocalized with CD43 in the uropod. Biochemical analyses showed that ezrin and moesin coimmunoprecipitated with CD43 in T lymphoblasts. Furthermore, in these cells, the CD43-associated moesin increased after stimulation through CD43. The interaction of moesin and ezrin with CD43 was specifically mediated by the cytoplasmic domain of CD43, as shown by precipitation of both ERM proteins with a GST-fusion protein containing the CD43 cytoplasmic tail. Videomicroscopy analysis of homotypic cell aggregation induced through CD43 showed that cellular uropods mediate cell-cell contacts and lymphocyte recruitment. Immunofluorescence microscopy performed in parallel showed that uropods enriched in CD43 and moesin localized at the cell-cell contact areas of cell aggregates. The polarization and homotypic cell aggregation induced through CD43 was prevented by butanedione monoxime, indicating the involvement of myosin cytoskeleton in these phenomena. Altogether, these data indicate that CD43 plays an important regulatory role in remodeling T-cell morphology, likely through its interaction with actin-binding proteins ezrin and moesin. In addition, the redistribution of CD43 to the uropod region of migrating lymphocytes and during the formation of cell aggregates together with the enhancing effect of anti-CD43 antibodies on lymphocyte cell recruitment suggest that CD43 plays a key role in the regulation of cell-cell interactions during lymphocyte traffic.
Characterisation of benign lesions and carcinomas of the female breast in a sub-Saharan African population.
Carcinoma of the breast is the second most frequent tumour in African females. Breast carcinomas in African females appear about a decade earlier and follow a more aggressive clinical course than those in developed countries. To elucidate this difference we investigated 63 biopsied benign lesions of the female breast for their potential to malignant progression. We also performed histologic typing and grading of 184 female breast carcinomas received at the Muhimbili University Hospital in Dar es Salaam, Tanzania. Fibrocystic disease and fibroadenomas were the most frequent lesions. The majority of patients with fibrocystic disease had no proliferative lesion and thus were not at a significantly increased risk of developing breast carcinomas. For fibroadenomas, no indication for precancerous lesions was found. The vast majority of breast carcinomas investigated were invasive. As a striking feature, the majority of those studied (66%) were of the non-special type (NST), displaying a more aggressive behaviour than the remaining tumours of the special type (ST). In the group of ST tumours, cribriform types constituted 41% of the cases which may be a special feature of the carcinomas in African females. Among the NST, the tumours were either of grade II or grade III, whereas in ST, 25% of the cases were of grade I. Since histology observed in this study is comparable to that seen in patients from the Western society, late hospital presentation with advanced tumour stages may be a major reason for differences in clinical behaviour between African and Western females. A genetic factor, however, may be an important contributing factor.
Abnormal surface expression of sialoglycans on B lymphocyte cell lines from patients with carbohydrate deficient glycoprotein syndrome I A (CDGS I A).
The carbohydrate-deficient glycoprotein syndromes (CDGS) are genetic, multisystemic diseases characterized by deficiencies in the glycosylation of many secretory glycoproteins, lysosomal enzymes, and possibly cell surface glycoproteins resulting in central nervous system abnormalities and frequent early death by infection. Here we examined whether membranous glycoconjugates of lymphocytes are affected by this disorder. For this, we analyzed cell surface-expressed sialoglycans of Epstein Barr virus (EBV)-transformed B cell lines derived from peripheral B lymphocytes of several patients with CDGS I A. These CDG-LCL (lymphoblastoid cell lines) expressed differentiation markers comparable to those of other EBV-transformed B cell lines. No apparent defects in the gross glycosylation process of defined complex glycosylated proteins such as the surface-expressed major histocompatibility complex class I glycoprotein or secreted immunoglobulin (IgM) were identified. However, using a novel flow cytometric enzyme assay to measure cell surface alpha2,6 sialylation on live cells we found that CDG-LCL express less alpha2,6 sialylated glycans in comparison to other EBV-transformed B cell lines. Also, CDG-LCL bound less of the B lymphocyte lectin CD22, specific for alpha2,6 sialylated lactosamines and known to modulate B cell receptor mediated signaling, as demonstrated by using a soluble CD22-immunoglobulin fusion protein in flow cytometry. CDG-LCL showed stronger surface staining with the monoclonal antibody 1B2 which detects a distinct group of surface-expressed lactosaminyl epitopes. After pretreatment with neuraminidase of Newcastle disease virus (NDVN) it became apparent that in CDG-LCL a significantly larger portion of the 1B2 epitopes was sialylated in alpha2,3 linkage as compared to other B cell lines. Intracellular alpha2,6 sialyltransferase activity as well as polymerase chain reaction products specific for four different sialyltransferases did not significantly differ in CDG-LCL as compared to other EBV-B cell lines. Differences in sialylation may be caused by the respective oligosaccharide core structures available for alpha2,6 or alpha2,3 sialylation in CDG-LCL. Therefore, lymphocytes derived from CDGS patients have distinct deviations in their surface-expressed lactosaminoglycan structures which may affect functions as exemplified by reduced interactions of CD22 with its ligands.
Moesin interacts with the cytoplasmic region of intercellular adhesion molecule-3 and is redistributed to the uropod of T lymphocytes during cell polarization.
During activation, T lymphocytes become motile cells, switching from a spherical to a polarized shape. Chemokines and other chemotactic cytokines induce lymphocyte polarization with the formation of a uropod in the rear pole, where the adhesion receptors intercellular adhesion molecule-1 (ICAM-1), ICAM-3, and CD44 redistribute. We have investigated membrane-cytoskeleton interactions that play a key role in the redistribution of adhesion receptors to the uropod. Immunofluorescence analysis showed that the ERM proteins radixin and moesin localized to the uropod of human T lymphoblasts treated with the chemokine RANTES (regulated on activation, normal T cell expressed, and secreted), a polarization-inducing agent; radixin colocalized with arrays of myosin II at the neck of the uropods, whereas moesin decorated the most distal part of the uropod and colocalized with ICAM-1, ICAM-3, and CD44 molecules. Two other cytoskeletal proteins, beta-actin and alpha-tubulin, clustered at the cell leading edge and uropod, respectively, of polarized lymphocytes. Biochemical analysis showed that moesin coimmunoprecipitates with ICAM-3 in T lymphoblasts stimulated with either RANTES or the polarization- inducing anti-ICAM-3 HP2/19 mAb, as well as in the constitutively polarized T cell line HSB-2. In addition, moesin is associated with CD44, but not with ICAM-1, in polarized T lymphocytes. A correlation between the degree of moesin-ICAM-3 interaction and cell polarization was found as determined by immunofluorescence and immunoprecipitation analysis done in parallel. The moesin-ICAM-3 interaction was specifically mediated by the cytoplasmic domain of ICAM-3 as revealed by precipitation of moesin with a GST fusion protein containing the ICAM-3 cytoplasmic tail from metabolically labeled Jurkat T cell lysates. The interaction of moesin with ICAM-3 was greatly diminished when RANTES-stimulated T lymphoblasts were pretreated with the myosin-disrupting drug butanedione monoxime, which prevents lymphocyte polarization. Altogether, these data indicate that moesin interacts with ICAM-3 and CD44 adhesion molecules in uropods of polarized T cells; these data also suggest that these interactions participate in the formation of links between membrane receptors and the cytoskeleton, thereby regulating morphological changes during cell locomotion.