Search PubMed⌕ Search

Biomedical subjects

C G Figdor

Publications and source records attributed to C G Figdor.

At least 91 records · Page 5Linked to original sources
PubMed1997

Cloning, expression and tissue distribution of the murine homologue of the melanocyte lineage-specific antigen gp100.

Melanocyte lineage-specific antigens, like gp100, have been shown to be recognized by tumour-infiltrating lymphocytes isolated from melanoma patients. Therefore these antigens might be used as targets for specific anti-melanoma immunotherapy. To investigate this potential in syngeneic mouse models, we cloned and characterized the murine homologue of gp100 from a B16 murine melanoma cDNA library. The isolated cDNA clone encodes a protein of 626 amino acids, sharing 79.7% sequence homology with human gp100. Expression of murine gp100 was restricted to cells of the melanocyte lineage, as determined by Northern and Western analysis. However, like human gp100, reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed low levels of transcription of the murine gp100 gene in all the cell lines and normal tissues tested. In contrast, murine tyrosinase, another melanocyte differentiation antigen, mimics human tyrosinase expression and did show absolute melanocyte lineage-specific expression. The characterization of murine gp100 will allow investigation of anti-gp100 immune responses in C57BL/6 mice using the syngeneic B16 tumour model and the possible adverse effects of such immunity on normal melanocytes.

Amino Acid Sequence↗
PubMed1996

Induction of LFA-1 on pluripotent CD34+ bone marrow cells does not affect lineage commitment.

Leukocyte function associated antigen 1 (LFA-1) is an adhesion molecule indispensable in immune and inflammatory reactions, but its role in hematopoiesis remains obscure. Since LFA-1 is predominantly expressed by leukocytes, it is considered as a marker of late stage stem cell maturation when expressed on CD34+ bone marrow cells, and represents more mature hematopoietic progenitor cells. We observed that freshly isolated CD34+ bone marrow cells express LFA-1, and that the level of expression is highly variable. Interestingly, the expression of LFA-1 specific activation epitope L16 on these cells is low, even after culture. This demonstrates the LFA-1 is not activated, as was confirmed by low adhesion to ICAM-1. Culturing sorted CD34+ LFA-1+ cells in single cell per well assays in medium supplemented with SCF, Epo, IL-3, Il-6, GM-CSF, and G-CSF revealed that they gave rise to dispersed macrophage-like colonies, supporting the notion that CD34+LFA-1+ cells indeed consist of a mature committed cell population. In contrast, sorted CD34+LFA-1- cells had high proliferative potential and developed into large multilineage colonies within 14 days of culture. Unanticipated, in time course experiments we observed that these CD34+LFA-1- cells expressed LFA-1 within 24 hours upon culture. This induction was neither caused by the monoclonal antibody used to tag CD34 cells, nor dependent on growth factors present in the medium. These findings demonstrate that two populations of CD34+LFA-1+ cells can be discriminated: leukocyte lineage committed CD34+ cells in freshly isolated bone marrow cells, and multipotent CD34+ cells that acquired LFA-1 upon in vitro culture. These in vitro findings support the hypothesis that once contacts with bone marrow stroma are lost, LFA-1 is upregulated by default, due to the lack of negative regulating signals from stromal cells. This might also explain the widely variable expression of LFA-1 as a result of crowding of cells in the bone marrow with subsequent loss of contact with stroma and upregulation of LFA-1, providing those cells with adhesion receptors enabling migration in the periphery.

Antigens, CD34↗
PubMed1996

Antibodies that selectively inhibit leukocyte function-associated antigen 1 binding to intercellular adhesion molecule-3 recognize a unique epitope within the CD11a I domain.

Several studies indicate that the I domain located in the alpha chain (CD11a) of leukocyte function-associated antigen-1 (LFA-1; CD11a/CD18) plays an essential role in ligand recognition. We recently identified three distinct epitopes (IdeA, IdeB, and IdeC) within the CD11a I domain, recognized by antibodies that block binding of LFA-1 to intercellular adhesion molecules (ICAM) 1, 2, and 3. In the present study, we used a series of human/murine CD11a I domain chimeras, to localize a fourth I domain epitope (IdeD), recognized by three independently derived anti-CD11a antibodies that selectively block the binding of LFA-1 to ICAM-3, but not to ICAM-1. The IdeD epitope depended on human CD11a residues Asp182 and Ser184 and was not present in CD11b or CD11c. Although mutation of Asp182 and Ser184 failed to abolish ICAM-3 adhesion of LFA-1 transfectants, alignment of these residues with the crystal structure of the CD11a I domain suggested that the IdeD epitope is located in close proximity to residues (Ile126 and Asn129) recently implicated in the ICAM-3 binding site. Interestingly, the IdeB and IdeC epitopes appeared to be in close proximity of a divalent cation binding pocket within the CD11a I domain that regulates both ICAM-1 and ICAM-3 adhesion. Taken together, these data indicate that distinct regions of the CD11a I domain contain epitopes for antibodies that either selectively inhibit binding of LFA-1 to ICAM-3, or interfere with both ICAM-1 and ICAM-3 binding of LFA-1.

Amino Acid Sequence↗
PubMed1996

Critical amino acids in the lymphocyte function-associated antigen-1 I domain mediate intercellular adhesion molecule 3 binding and immune function.

We have identified amino acid residues within the evolutionarily conserved I domain of the alpha-chain (CD11a) of the leukocyte integrin leukocyte function-associated antigen (LFA) 1 that are critical for intercellular adhesion molecule (ICAM) 3 (CD50) binding. ICAM-3, a ligand of LFA-1, is thought to mediate intercellular adhesion essential for the initiation of immune responses. Using a panel of human/murine I domain chimeras and point mutants, we observed that the Ile-Lys-Gly-Asn motif, located in the NH2-terminal part of the CD11a I domain, is required for ICAM-3 but not ICAM-1 binding. These findings demonstrate that the I domain of CD11a contains distinct functional subdomains for ligand specific binding. An aspartic acid located at position 137, which is essential to ICAM-1/LFA-1 interactions (Edwards, C.P., M. Champe, T. Gonzalez, M.E. Wessinger, S.A. Spencer, L.G. Presta, P.W. Berman, and S.C. Bodary. 1995. J. Biol. Chem. 270:12635-12640), was also critical for ICAM-3 binding, whereas Ser at position 139 did not effect ICAM-1 or ICAM-3 binding. A synthetic peptide containing the Ile-Lys-Gly-Asn motif inhibited ICAM-3-dependent adhesion and proliferation of T cells at micromolar concentrations, suggesting that this peptide interferes with immune recognition. These observations underscore the importance of ICAM-3 in leukocyte function, and may lead to development of a new category of immunosuppressive agents.

Amino Acid Sequence↗
PubMed1996

Activation and increased expression of adhesion molecules on peripheral blood lymphocytes is a mechanism for the immediate lymphocytopenia after administration of OKT3.

We investigated the mechanism by which antihuman CD3 monoclonal antibodies of the isotypes IgG2a (eg, OKT3) and IgA (eg, IXA) can induce the rapid disappearance of virtually all circulating T lymphocytes. We hypothesize that upregulation of adhesion molecules on the lymphocyte membrane contributes to this effect. However, this hypothesis is difficult to test, because of the inherent lymphocytopenia and/or shifts in lymphocyte populations between intra and extra-vascular compartments. Therefore, studies in vitro were performed, as well. Analysis of peripheral blood lymphocytes isolated at several times after addition of OKT3 or IXA to whole blood of healthy individuals showed an immediate increase in the proportion of T cells expressing NKI-L16, an activation epitope on CD11a/CD18. Likewise, an increase in CD11b/CD18 expression occurred. In parallel experiments, a transiently increased adhesion of T cells to endothelial cell monolayers was observed. This adhesion could be completely blocked by anti-CD18 or anti-CD11a monoclonal antibodies and only partly by an anti-CD11b antibody. Our data indicate that upregulation of activation epitopes of CD11a/CD18, as well as increased expression of CD11b/CD18 on T lymphocytes, may result in increased adhesion of these cells to intercellular adhesion molecule-1 (ICAM-1) and ICAM-2 on vascular endothelium. This phenomenon may, at least, partly explain the rapidly occurring peripheral lymphocytopenia observed in vivo.

Adult↗
PubMed1996

Competition between lymphocyte function-associated antigen 1 (CD11a/CD18) and Mac-1 (CD11b/CD18) for binding to intercellular adhesion molecule-1 (CD54).

Both human integrin receptors Mac-1 (CD11b/CD18,CR3)and lymphocyte function-associated antigen (LFA)-1 (CD11a/CD18) have been demonstrated to bind human intercellular adhesion molecule-1 (ICAM-1) (CD54). Here we show that LFA-1 and Mac-1 can bind to ICAM-1 in the mouse as well. Interestingly, we observed that binding of murine LFA-1 dominates over Mac-1 for binding to ICAM-1. Using three different murine macrophage cell lines that express distinct levels of LFA-1 and Mac-1 on their cell surface, we could only detect Mac-1-dependent adhesion to ICAM-1 when little or no LFA-1 is expressed on the cell surface. When LFA-1 and Mac-1 are expressed at similar levels, the LFA-1/ICAM-1 interaction dominates over Mac-1/ICAM-1 interaction, indicating that there is a competition of LFA-1 and Mac-1 for ICAM-1 binding.

Animals↗
PubMed1996

Dendritic cells in immune response induction.

The study of dendritic cells (DCs) has seen a rapid expansion in recent years, and their importance within the immune system is now widely recognized. Along with B lymphocytes and mononuclear phagocytes, DCs make up what are known as the professional antigen-presenting cells (APCs). These are cells which are capable of highly efficiently presenting antigens to the immune system in the context of both major histocompatibility complex class I and class II molecules. What makes DCs stand out from other professional APCs, however, is their seemingly unique ability to present antigen to T lymphocytes which have had no previous contact with antigen. This gives DCs central role in the initiation of immune responses, and creates possibilities for their exploitation in the development of therapeutic strategies against tumors and other diseases. What are the characteristics of DCs which enable them to carry out their specialized function? This is a question which is currently gaining much interest. While higher expression levels of the antigen-presentation machinery may account for this, there may also be as yet unidentified mechanisms at work. In this review, we will discuss the evidence for DC-mediated priming of both CD4+ and CD8+ naive T cells, both in vitro and in vivo, current ideas on how DCs achieve their potent function and the implications for the design and execution of immunotherapeutic strategies.

Animals↗
PubMed1996

pMel17 is recognised by monoclonal antibodies NKI-beteb, HMB-45 and HMB-50 and by anti-melanoma CTL.

Recently, we cloned the cDNA encoding the melanocyte lineage-specific antigen gp100 and demonstrated that gp100 is recognised by three different monoclonal antibodies (MAbs) used to diagnose malignant melanoma. In addition, we showed that tumour-infiltrating lymphocytes (TIL 1200) from a melanoma patient reacted specifically with cells transfected with the gp100 cDNA. Molecular characterisation of the gp100 cDNA revealed that the gp100 antigen is highly homologous, but not identical, to another melanocyte-specific protein, pMel17. Here, we report that cells transfected with pMel17 cDNA also react with all three MAbs used to diagnose malignant melanoma, NKI-beteb, HMB-45 and HMB-50. Moreover, pMel17 transfectants are specifically lysed by TIL1200. These data demonstrate that antigenic processing of both gp100 and pMel17 give rise to peptides seen by anti-melanoma cytotoxic T lymphocytes (CTL) and are therefore potential targets for immunotherapy of malignant melanoma.

Amino Acid Sequence↗
PubMed1995

Generation of antimelanoma cytotoxic T lymphocytes from healthy donors after presentation of melanoma-associated antigen-derived epitopes by dendritic cells in vitro.

MHC class I-restricted CTLs specific for antigens expressed by malignant cells are an important component of immune responses against human cancer. Recently, in melanoma a number of melanocyte differentiation antigens have been identified as potential tumor rejection antigens. In the present study, we show that by applying peptide-loaded dendritic cells, induced by granulocyte-macrophage colony-stimulating factor and interleukin 4 from peripheral blood monocytes of healthy donors, we were able to elicit melanoma-associated antigen-specific CTL in vitro. We demonstrate the induction of CTLs directed against HLA-A2.1 presented epitopes derived from tyrosinase, gp100, and Melan A/MART-1. Apart from lysis of peptide-loaded target cells, these CTLs displayed reactivity with HLA-A2.1+ melanoma tumor cell lines and cultured normal melanocytes endogenously expressing the target antigen. These data indicate that these CTLs recognize naturally processed and presented epitopes and that precursor CTLs against melanocyte differentiation antigens are present in healthy individuals. The ability to generate tumor-specific CTLs in vitro, using granulocyte-macrophage colony-stimulating factor/interleukin 4-induced dendritic cells, illustrates the potential use of this type of antigen-presenting cells for vaccination protocols in human cancer.

Amino Acid Sequence↗
PubMed1995

Occurrence and a possible mechanism of penetration of natural killer cells into K562 target cells during the cytotoxic interaction.

The cytotoxic interaction between cloned human Natural Killer (NK) cells and K562 target cells was studied using confocal laser scanning microscopy (CLSM) and conventional fluorescence microscopy. We observed, using fixed as well as living cells, the occurrence of (pseudo) emperipolesis during the interaction. About 30% of conjugated NK cells penetrated, partly or completely, into the target cells (in-conjugation). Virtually all in-conjugated target cells exhibited polymerized actin. Killer cells of in-conjugates were frequently seen approaching the target cell nucleus or aligning along it. If the cytotoxic process was inhibited by the absence of calcium neither actin polymerization nor in-conjugation were observed. A kinetic study showed that in-conjugation starts somewhat later than actin polymerization but still within a few minutes after addition of calcium to conjugates previously formed in the absence of calcium. The presence of cytochalasin D (an inhibitor of actin polymerization) completely inhibited in-conjugation and partly reduced the cytotoxic activity. Zinc ions (endonuclease inhibition) inhibited in-conjugation and decreased the total number of target cells with polymerized actin in a concentration dependent manner. Cytotoxic activity was also reduced but not as efficiently as in-conjugation. Our study demonstrates that in-conjugation represents a significant fraction of the cytotoxic interaction. The results indicate that it may be a consequence of an actin polymerization and endonuclease activity dependent part of a cytotoxic mechanism.

Actins↗
PubMed1995

Identification of a novel peptide derived from the melanocyte-specific gp100 antigen as the dominant epitope recognized by an HLA-A2.1-restricted anti-melanoma CTL line.

Cytotoxic T lymphocytes (CTL) reactive with human melanoma tumor cells occasionally display cross-reactivity with normal melanocytes. Previously, we identified the melanocyte lineage-specific antigen gp 100 that is expressed by both melanoma cells and normal melanocytes, as a target antigen for tumor-infiltrating lymphocytes derived from a melanoma patient (TIL 1200). Here, we demonstrate that the oligoclonal HLA-A2.1-restricted TIL 1200 line is reactive with 2 distinct peptides derived from the gp 100 protein. Apart from the peptide corresponding to gp 100 amino acids 457-466, we identified the gp 100 peptide 154-162 as a second epitope recognized by TIL 1200. A 100-fold lower concentration of this novel gp 100 peptide was required for target-cell sensitization compared to peptide 457-466, indicating that the 154-162 peptide is the dominant gp 100 epitope for TIL 1200. Together with the recently described gp 100 280-288 epitope, 3 distinct CTL epitopes have now been identified in gp 100, all presented in the context of HLA-A2.1. Therefore, gp 100 is an attractive target antigen in the development of immuno-therapeutic protocols against melanoma.

Amino Acid Sequence↗
PubMed1995

Antibodies that activate beta 2 integrins can generate different ligand binding states.

A human erythroleukemic cell line (K562) that does not normally express beta 2 integrins has been transfected with the genes encoding these integrins. The resulting cell lines show minimal background adhesion but can be stimulated to bind to appropriate substrates when activated with either of two different antibodies to CD18. The two antibodies appear to generate different ligand binding states in LFA-1 such that different members of the ICAM family are recognized. Antibody-activated complement receptor type 3 and p150,95-transfected cells bind protein-coated surfaces, although they require slightly different activation conditions for optimal binding.

Antibodies, Monoclonal↗
PubMed1995

Allograft rejection in cattle with bovine leukocyte adhesion deficiency.

In the present investigation cell-mediated immunity in animals with bovine leukocyte adhesion deficiency (BLAD) was studied by means of skin transplantation experiments. Autograft and allograft behaviour in animals with BLAD was compared with the behaviour of simultaneously transplanted autografts and allografts in healthy controls. Allograft survival time was prolonged in three BLAD cattle (28, 30, and 72 days) compared to six healthy controls (12-14 days). When transplantations were repeated on one animal with BLAD using skin grafts from the same donor, accelerated rejection was observed (allograft survival time decreased from 72 days at primary to 35 days at secondary and to 21 days at tertiary transplantation), suggesting the development of immunological memory. Graft-infiltrating lymphocytes that were obtained from allograft biopsies during the period of rejection, were shown to be from recipient origin (beta 2-integrin negative). Our findings demonstrate that, although prolonged allograft survival is observed in cattle with BLAD, skin allografts are ultimately rejected.

Animals↗
PubMed1995

Ins and outs of LFA-1.

Leukocyte function-associated molecule 1 (LFA-1) is an integrin that plays a major role in the immune system. Recent findings demonstrate that LFA-1 has a two-way signaling function, mediating cell adhesion and stimulating intracellular processes at the same time. Here, Marijke Lub, Yvette van Kooyk and Carl Figdor discuss the 'inside-out' and 'outside-in' signaling properties of LFA-1, as a prototype leukocyte integrin, in normal and malignant T cells. They integrate data into a model that highlights the role of the cytoskeleton in the regulation of LFA-1.

Animals↗
PubMed1995

Phenotypic and functional changes in peripheral blood monocytes during progression of human immunodeficiency virus infection. Effects of soluble immune complexes, cytokines, subcellular particulates from apoptotic cells, and HIV-1-encoded proteins on monocytes phagocytic function, oxidative burst, transendothelial migration, and cell surface phenotype.

We postulated that changes in the cell surface display of molecules that facilitate cell-cell and cell-matrix adhesions may reflect the changing immunosurveillance capacity of blood monocytes during progression of human immunodeficiency virus (HIV) infections. In Centers for Disease Control (CDC) stage A patients, whose monocytes' ability to phagocytose bacteria and generate reactive oxygen intermediates is often increased, the frequency of monocytes expressing CD49d, HLA-DP, HLA-DQ, and an activation epitope of CD11a/CD18 was increased and monocyte transendothelial migration was unimpaired. In CDC stage B/C patients, whose monocytes' ability to phagocytose bacteria and migrate across confluent endothelial monolayers was diminished, surface expression of CD49e and CD62L and the percentage of monocytes expressing CD18, CD11a, CD29, CD49e, CD54, CD58, CD31, and HLA-I were significantly decreased. Incubating normal donor monocytes with immune complexes in vitro reproduced the phenotypic and functional abnormalities seen in stage B/C patients. By contrast, in vitro stimulation with subcellular particulates released by apoptotic lymphocytes reproduced changes seen in stage A patients' monocytes. Although circulating monocytes appear to be activated at all stages, these data suggest that the high levels of circulating immune complexes, found predominantly in the later stages of HIV infection, may be particularly instrumental in reducing the monocyte's capacity to maintain surveillance against infection.

Antigen-Antibody Complex↗
PubMed1995

KIM127, an antibody that promotes adhesion, maps to a region of CD18 that includes cysteine-rich repeats.

A series of fusion proteins have been generated between human and mouse CD18. These proteins have been used to carry out preliminary mapping studies on a number of anti-CD18 antibodies including KIM127 an antibody that promotes CD18-dependent adhesion. This antibody maps to a region of the CD18 molecule between amino acids 406 and 570 in a region containing cysteine-rich repeats.

Animals↗
PubMed1994

Potential indirect anti-inflammatory effects of IL-4. Stimulation of human monocytes, macrophages, and endothelial cells by IL-4 increases aminopeptidase-N activity (CD13; EC 3.4.11.2).

IL-4 up-regulates various monocytic properties that are associated with pro-inflammatory functions. Paradoxically, IL-4 may also act as an anti-inflammatory agent by down-regulating the production of several inflammatory mediators. As the activity of some mediators has recently been shown to be regulated by peptidases, we examined whether IL-4 was able to modulate the expression of a cell membrane-associated peptidase, aminopeptidase-N (CD13). IL-4 caused a dose-dependent increase in the expression of CD13 Ag on highly purified human blood monocytes. Maximal expression was observed around 48 h of culture. This IL-4-induced increase was completely blocked by anti-IL-4 antiserum. Furthermore, the increase in surface expression was preceded by increased mRNA levels of CD13, which was maximal around 24 h of culture. We also observed that CD13-mediated leucine-aminopeptidase activity of monocytes was induced by IL-4. Other CD13-expressing cells were also sensitive to IL-4, as CD13 Ag expression and CD13 mRNA levels were up-regulated in human alveolar macrophages and endothelial cells upon IL-4 treatment. The increased expression of cell membrane aminopeptidase-N represents a potentially increased cellular ability to inactivate inflammatory mediators. Therefore, these findings represent further evidence of IL-4-mediated anti-inflammatory actions. We postulate that up-regulation of aminopeptidase-N expression may be an indirect mechanism of IL-4 to modulate the action of bioactive peptides. This mechanism may underlie, at least partially, the anti-inflammatory effects of IL-4 in vivo.

Aminopeptidases↗