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D Hanau

Publications and source records attributed to D Hanau.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Langerhans cells and presentation of antigens].

Epidermal Langerhans cells express only very few Class I major histocompatibility complex (MHC) antigens, whose ability to present peptides released from the breakdown of endogenous proteins has not been investigated to date. Langerhans cells strongly express a "nonconventional" Class I molecule, the CD1a antigen. The role played by this antigen on the surface of Langerhans cells remains unelucidated: either release or uptake of peptides derived from the body has been speculated. Langerhans cells also express Class II MHC antigens and in vitro freshly recovered Langerhans cells are capable of capturing antigens, processing them and presenting the resulting peptides associated with Class II MHC molecules to immunocompetent cells. This property is not, however, permanent. Cultured Langerhans cells are no longer capable of processing antigens because they lose their ability to (i) acidify endosomes and (ii) produce the alpha, beta and invariant chains of class II MHC molecules. Cultured Langerhans cells acquire the capacity of stimulating T lymphocytes. This contrast between the in vitro properties of freshly recovered and cultured Langerhans cells may reflect in vivo differences between epidermal Langerhans cells and Langerhans cells which have migrated to regional lymph nodes.

Epidermis↗
PubMed1991

Normal ADP-induced aggregation and absence of dissociation of the membrane GP IIb-IIIa complex of intact rat platelets pretreated with EDTA.

ADP-induced platelet aggregation requires the presence of external calcium and fibrinogen. When human platelets are incubated for 30 min at 37 degrees C with 5 mM EDTA and then resuspended in a calcium containing medium, they lose their ability to bind fibrinogen and to aggregate in response to ADP stimulation. Under these conditions, the effect of EDTA is irreversible and accompanied by dissociation of the glycoprotein (GP) IIb-IIIa complex into its free subunits, GP IIb and GP IIIa. We studied the effect of incubation of intact rat platelets with 5 mM EDTA at 37 degrees C from 30 to 120 min. EDTA treated rat platelets showed normal aggregation in response to 5 microM ADP in the presence of added purified rat fibrinogen and bound 125I-labeled rat fibrinogen at the same rate and magnitude after stimulation with 5 microM ADP as untreated platelets. Control and EDTA treated rat platelets, labeled or not with 125I and solubilized in Triton X-100, had a similar pattern of immunoprecipitates after crossed immunoelectrophoresis (CIE) analysis. The rat GP IIb-IIIa arc was located by incorporation of an 125I-labeled polyclonal anti-human GP IIb-IIIa antibody. In contrast, in experiments using rat platelet lysates, we demonstrated that the rat GP IIb-IIIa is a Ca(2+)-dependent heterodimer as it was dissociated by EDTA. Using SDS-PAGE and two-dimensional SDS-PAGE, the rat GP IIb-IIIa complex was found to have characteristics similar to the human complex with the exception that the light chain of the rat GP IIb was undetectable after 125I surface labeling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1991

Ultrastructural similarities between epidermal Langerhans cell Birbeck granules and the surface-connected canalicular system of EDTA-treated human blood platelets.

Birbeck granules characterize under the electron microscope epidermal Langerhans cells. These distinctive pentalaminar organelles are indeed not detectable in the possible precursors of human Langerhans cells and tend to disappear in cultured human Langerhans cells. The mechanisms that lead to the appearance of Birbeck granules in epidermal Langerhans cells and to their later disappearance still remain unknown. In the present study we show that the more or less dilated elements of the surface-connected canalicular system of human blood platelets collapse after EDTA treatment. Made up of two parallel limiting membrane and central irregular striated density, these elements show great ultrastructural similarities with the Birbeck granules of human epidermal Langerhans cells. These platelet morphologic changes i) are directly dependent on the EDTA-induced dissociation of the glycoprotein GP IIb-IIIa, the platelet-specific calcium-dependent heterodimer complex, member of the beta 3 integrin subfamily (alpha IIb beta 3) and ii) apparently result from a cross-linking of the dissociated glycoproteins. These findings lead us to propose that in the same manner cells of the Langerhans lineage, on reaching the epidermis, will find themselves in contact with an epidermal specific ligand. Interactions between this epidermal ligand and Langerhans cell receptors could then induce, all along the circuit taken by the ligand-receptor complexes, morphologic modifications, i.e., appearance of structures of Birbeck granule type.

Blood Platelets↗
PubMed1991

Interaction of human epidermal Langerhans cells with HIV-1 viral envelope proteins (gp 120 and gp 160s) involves a receptor-mediated endocytosis independent of the CD4 T4A epitope.

The CD4 molecule is known to be the preferential receptor for the HIV-1 envelope glycoprotein. Epidermal Langerhans cells are dendritic cells which express several surface antigens, among them CD4 antigens. To clarify the exact role of CD4 molecules in Langerhans cell infection induced by HIV-1, we investigated the possible involvement of the interactions between HIV-1 gp 120 or HIV-1 gp 160s (soluble gp 160) and Langerhans cell surface. We also assessed the expression of CD4 molecules on Langerhans cell membranes dissociated by means of trypsin from their neighbouring keratinocytes. The cellular phenotype was monitored using flow cytometry and quantitative immunoelectron microscopy. We reported that human Langerhans cells can bind the viral envelope proteins (gp 120 or gp 160s), and that this binding does not depend on CD4 protein expression. This binding is not blocked by anti-CD4 monoclonal antibodies. We show that a proportion of gp 120/gp 160s-receptor complexes enters Langerhans cells by a process identified as a receptor-mediated endocytosis. The amount of surface bound gp 120/gp 160s is not consistent with the amount of CD4 antigens present on Langerhans cell membranes. Gp 120/gp 160s binding sites on Langerhans cell suspensions appeared to be trypsin resistant, while CD4 antigens (at least the epitopes known to bind the HIV-1) are trypsin sensitive. A burst of gp 120 receptor expression was detected on 1-day cultured Langerhans cells while CD4 antigens disappeared. These findings lead to the most logical conclusion that binding of gp 120/gp 160s is due to the presence of a Langerhans cell surface molecule different from CD4 antigens.

Antigens, Surface↗
PubMed1990

Human epidermal Langerhans cells express only the 40-kilodalton Fc gamma receptor (FcRII).

In man, three distinct classes of receptors for the Fc fragments of IgG (FcRI, II, III) have been defined. The FcRI has a Mr of about 72 kDa, binds human IgG-coated E, and is recognized by mAb such as 32. The FcRII has a Mr of 40 kDa, binds murine IgG1-coated E, and reacts with the mAb IV.3 and CIKM5, which recognize CDw32 moieties. Lastly, the FcRIII has a Mr of 50 to 70 kDa and is recognized by anti-CD16 mAb. In the present study we have shown that i) only murine IgG1-coated E form rosettes with 49 +/- 1.5% (mean +/- SEM, n = 9) of CD1a+ epidermal cells (EC) (which represent Langerhans and indeterminate cells) and that ii) the mAb anti-FcRII CIKM5 prevents this rosette formation. Among the mAb reacting with the three different types of FcR, only those recognizing FcRII i) stain about 55 +/- 1.5% (mean +/- SEM, n = 9) of the CD1a+ EC and ii) reveal the presence of dendritic cells in epidermal sheets obtained by suction blister. Under the electron microscope i) apparently all the cells forming rosettes or reacting with the gold-labeled anti-FcRII mAb (CIKM5 or the F(ab) fragment of IV.3) contained Birbeck granules and ii) the gold-labeled mAb were internalized in unfixed Langerhans cells by receptor-mediated endocytosis and accumulated in lysosomes. Labeling by the anti-FcRII mAb of the CD1a+ cells in suspension disappears after 48 h of culture. All these observations strongly suggest that CD1a+ EC express only the FcRII. This conclusion was confirmed by immunoprecipitation experiments, whereas no specific immunoprecipitate was noted with the anti-FcRI or anti-FcRIII mAb, the anti-FcRII mAb immunoprecipitated a protein of Mr 40 kDa.

Antibodies, Monoclonal↗
PubMed1990

Fc receptors of human Langerhans cells.

Receptors for the Fc fragment of immunoglobulins (Fc R) exhibit specificities for a wide variety of immunoglobulin classes and subclasses. In humans, at least three distinct classes of receptors for the Fc fragments of IgG (Fc gamma RI, II, III) and two classes of receptors for the Fc fragments of IgE (Fc epsilon RI, II) have been characterized. These classes were largely defined on the basis of their affinities for different immunoglobulin subclasses and their reactivities with monoclonal anti-receptor antibodies. Among these FcR, in healthy individuals, epidermal Langerhans cells (LC) express only the Fc gamma RII/CDw32. This FcR--a member of the immunoglobulin superfamily--is only present on about 50% of freshly isolated CD1a positive cells, as determined by rosette assays. It has a Mr of 40 kDa, is trypsin resistant, binds polymeric human IgG and murine IgG1-coated erythrocytes, and reacts with anti-CDw32 monoclonal antibodies (MoAb). LC internalize Fc gamma RII by receptor-mediated endocytosis. After 48 h of culture, human LC loose their Fc gamma RII, as revealed by flow cytometry. While the function(s) of the Fc gamma RII on human LC remain(s) unknown, this receptor may be primarily involved, like the Fc gamma RII present on mouse macrophages, in the clearance of extra-cellular immune complexes. In patients with atopic dermatitis having an elevated IgE serum level, beside an increased expression of the Fc gamma RII by LC located on lesional skin, IgE-bearing epidermal and dermal LC are present, again essentially on lesional skin. Double immunolabeling on cryosections reveals that on lesional skin only about 50% of the epidermal CD1a positive cells bear IgE. This capacity of LC to bind IgE molecules appears to be due to the presence of a specific Fc epsilon R. While the class of this Fc epsilon R still remains unclear, it appears to have some particularities: i) an associated expression with the CD1a antigen, ii) an affinity for IgG, and iii) a trypsin resistance. In vitro, human recombinant interleukin (IL)-4 and/or interferon (IFN)-gamma are able to induce the synthesis and expression of Fc epsilon RII/CD23 on a percentage of normal human epidermal LC. This Fc epsilon RII seems to be functional since it binds IgE molecules, this binding being prevented by preincubation with anti-CD23 MoAb.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Platelets↗
PubMed1989

ATPase and morphologic changes in Langerhans cells induced by epicutaneous application of a sensitizing dose of DNFB.

We have previously described an ATPase Langerhans cell (LC) staining technique allowing progression from light to electron microscope observation. Using this technique we have studied, following epicutaneous application of a sensitizing dose of a hapten, 2,4-dinitro-1-fluorobenzene (DNFB), the fate of the epidermal LC located in the sensitization zone. We wanted to know, under the light microscope, if the density and/or morphology of the LC are modified by such a treatment and, under the electron microscope, what are the ultrastructural changes accompanying the possible light microscope modifications. Under the light microscope, the observation of LC during the 5 d necessary for the development of contact sensitivity to DNFB shows that their number drops in the course of the first 24 h to normalize again 3 d later. Under the electron microscope, observations over the first 24 h revealed that LC remained in the epidermis, but were ATPase-negative. The disappearance of the membrane ATPase activity took place while the LC presented an increased number of coated pits, coated vesicles, endosomes, and lysosome organelles which characterize, at the ultrastructural level, the process of receptor-mediated endocytosis (RME). Following RME, many Birbeck granules (BG) appeared in the cytoplasm. Thus, epicutaneous application of DNFB leads to an endocytic activation of LC. However, the ligand(s) and/or the cell-surface components, which probably internalize during the RME process, remain unknown.

Adenosine Triphosphatases↗
PubMed1989

Isolation of epidermal Langerhans cells.

Langerhans cells (LC) play an important role in the skin immune system. They are bone marrow-derived and function as the only accessory and antigen-presenting cells in the skin. Several techniques for enriching these cells have been devised, and four, including density gradient centrifugation, use of cell sorter, panning and immunomagnetic separation, are discussed. It is concluded that the most satisfactory method for isolation of LC is based on density gradient centrifugation and the most satisfactory for depletion of epidermal cell preparations for LC is based on the immunomagnetic principle.

Animals↗
PubMed1989

[HIV envelope proteins are bound by human epidermal Langerhans cells by a binding site which differs from the site on the CD4 molecule, and are internalized by receptor endocytosis].

Langerhans cells (LC) are epidermal dendritic cells which express several surface antigens among them the CD4 antigens. We investigated the fate of HIV envelope glycoproteins (gp 120 and gp 160) incubated with healthy human trypsinized LC in suspension. After trypsin treatment only the epitope for OKT4 appeared to be resistant. In absence of antigenic sites identified by OKT4A, Leu 3a or BL4, LC fixed and internalized gp 120 or gp 160 recombinant HIV proteins. This finding support the hypothesis that there exists at the surface of LC a second molecule which may act as a HIV receptor.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Appearance of Birbeck granule-like structures in anti-T6 antibody-treated human epidermal Langerhans cells.

We have previously demonstrated by immunogold labeling techniques that the T6 surface antigen of living human Langerhans cells (LC) of the skin is internalized by a process of receptor-mediated endocytosis (RME). Receptor-mediated endocytosis induced by the binding of the monoclonal anti-T6 antibody BL6 involves coated pits, coated vesicles, endosomes, the smooth endoplasmic reticulum, and lysosomes. After RME, gold-labeled Birbeck granules (BGs) appear in the cell center. In the present study, by modifying the experimental conditions but retaining the presence of gold-labeled BL6, we have observed (in addition to the above-mentioned gold-labeled organelles) images that appear to correspond to BG-like structures. These structures, like the intracytoplasmic BGs, are pentalaminar and gold-labeled, but they differ from the intracytoplasmic BGs by their attachment to the cell membrane, their length, the frequent presence of a coat, and by prolongation by one or more coated pits. Birbeck granule-like structures seem to result, at the ultrastructural level, from receptor ligand interactions and from modifications of the LC shape.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

T6 positive cells in the peripheral blood of burn patients: are they Langerhans cells precursors?

Peripheral blood mononuclear cells of 14 patients suffering thermal injury were separated by affinity chromatography on peanut agglutinin (PNA) coupled to Sepharose macrobeads. The resulting PNA positive subset was 14% of the total mononuclear population. About 30% of these cells were found to coexpress T6(CD1), Ia-like and the myeloid differentiation antigens My4(CDw14) and Mo1(CD11). In comparison, the PNA+ subset from normal blood donors (about 5% of total mononuclear cells) contained mature monocytes that were found to be T6 negative. Electron microscopic studies using immunogold labeling showed that the T6 positive cells were slightly smaller than monocytes but larger than the classical lymphocytes and had common morphologic features with the Langerhans cells of the skin. Considering that patients suffering extensive damage of the epidermis require fast renewal of all skin elements, it is possible that the cells we identified in their peripheral blood are the precursors of the Langerhans cells of the skin en route from bone marrow to the epidermis.

Adolescent↗
PubMed1988

A method for the rapid isolation of human epidermal Langerhans cells using immunomagnetic microspheres.

Because Langerhans and indeterminate cells are the only epidermal cells that express the specific CD1a surface antigen T6, we have used immunomagnetic monodisperse polymer microspheres for positive selection of human epidermal Langerhans and indeterminate cells. Epidermal cells in suspension are successively incubated with a murine monoclonal anti-T6 antibody of the IgG1 subclass and then with magnetic beads coated with a sheep anti-mouse IgG1. Rosetted cells are obtained and then easily separated from the non-rosetted cells using a magnet. The two cell fractions are characterized by phase contrast microscopy, immunofluorescence, electron microscopy, and the skin cell-lymphocyte reaction. All the rosetted cells (1.5 to 5% of the total epidermal cells) express T6 antigen by indirect immunofluorescence and under the electron microscope possess all the ultrastructural characteristics of Langerhans cells. Moreover, the rosetted Langerhans cells remain functional: Under the electron microscope they internalize by receptor-mediated endocytosis gold labeled anti-T6 antibody, and in the skin cell-lymphocyte reaction they stimulate allogeneic lymphocytes. In contrast, the rosette depleted cell fraction is deprived of T6 positive cells and unable to stimulate allogeneic lymphocytes. The immunomagnetic depletion of epidermal cells is a simple and rapid method to isolate functional human Langerhans cells with good yield and high purity (97%). This technique should be of value in the study of the pharmacology of Langerhans cells and in the investigation of the interactions of Langerhans cells with keratinocytes or lymphocytes.

Cell Count↗
PubMed1988

Epinephrine potentiates human platelet activation but is not an aggregating agent.

Epinephrine can in certain in vitro conditions induce the aggregation of human platelets and could play an important role in vivo in the appearance of thrombotic disorders when catecholamine levels are increased. This study examines some functional and biochemical responses to epinephrine. Epinephrine induces the aggregation and serotonin secretion of human platelets in citrated plasma. This is not due to a direct effect of citrate itself, such as the lowering of plasma free Ca2+ but more likely to the generation of traces of thrombin during blood collection, as suggested by abrogation of these platelet responses when hirudin was added before citrate. When washed human platelets suspended in Tyrode buffer containing 2 mM Ca2+, 0.35% albumin and apyrase, and 0.1-100 microM epinephrine were used, no shape change, aggregation, or secretion of serotonin was observed, nor was the platelet ultrastructure modified. Epinephrine does not modify platelet membrane fluidity, as studied with the lipophilic fluorescent probe trimethylammonium-diphenylhexatriene. It has no direct effect on fibrinogen binding to intact platelets, intracellular Ca2+ levels measured by quin2, or protein phosphorylation. Epinephrine potentiates the action of all types of aggregating agents on aggregation, secretion, intracellular Ca2+ levels, membrane fluidity, fibrinogen binding, or protein phosphorylation. These effects are mediated by alpha 2-adrenergic agonists and inhibited by alpha 2-adrenergic antagonists. This study shows that epinephrine alone does not induce modifications of morphology, metabolism, or function of intact and functional washed human platelets and that it cannot be considered per se as an aggregating agent. However, epinephrine interacts with alpha 2-adrenergic receptors on human platelets and potentiates biochemical and aggregatory responses induced by other platelet agonists.

Adenosine Diphosphate↗
PubMed1987

Human epidermal Langerhans cells cointernalize by receptor-mediated endocytosis "nonclassical" major histocompatibility complex class I molecules (T6 antigens) and class II molecules (HLA-DR antigens).

HLA-DR and T6 surface antigens are expressed only by Langerhans cells and indeterminate cells in normal human epidermis. We have previously demonstrated that T6 antigens are internalized in Langerhans cells and indeterminate cells by receptor-mediated endocytosis. This process is induced by the binding of BL6, a monoclonal antibody directed against T6 antigens. In the present study, using a monoclonal antibody directed against HLA-DR antigens, on human epidermal cells in suspension, we show that the surface HLA-DR antigens are also internalized by receptor-mediated endocytosis in Langerhans and indeterminate cells. Moreover, using immunogold double labeling, we demonstrate that T6 and HLA-DR antigens are internalized through common coated regions of the membrane of Langerhans or indeterminate cells. The receptor-mediated endocytosis that is induced involves coated pits and vesicles, receptosomes, lysosomes, and also, in Langerhans cells, the Birbeck granules. Thus, T6 antigens, which are considered to be "unusual" or "nonclassical" major histocompatibility complex class I molecules, and the major histocompatibility complex class II molecules, HLA-DR, are internalized in Langerhans and indeterminate cells through common receptor-mediated endocytosis organelles.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Human epidermal Langerhans cells internalize by receptor-mediated endocytosis T6 (CD1 "NA1/34") surface antigen. Birbeck granules are involved in the intracellular traffic of the T6 antigen.

Using immunogold staining of a suspension of living human epidermal cells to identify the Langerhans cell membrane-associated antigen T6 (revealed by the monoclonal antibody BL6), we have observed internalization of T6 antigen in Langerhans cells. This phenomenon is at least partly due to receptor-mediated endocytosis involving coated pits, coated vesicles, endosomes, the smooth endoplasmic reticulum, and lysosomes. These ultrastructural results suggest that T6 antigen may be part of a receptor site. Following receptor-mediated endocytosis, the appearance in the cell center of the first labeled Birbeck granules suggests that Birbeck granules could represent T6 intracellular transport organelles carrying T6 from the central part of the cell to an unknown destination.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1987

Internalization by receptor-mediated endocytosis of T6 (CD1 "NA1/34") surface antigen in T6 positive human cord blood cells (Langerhans cell precursors?).

A subset of T6 positive cells was recently separated from normal human cord blood mononuclear cells. It was shown to coexpress HLA-DR and myeloid differentiation antigens (Mo1, MY4). The phenotype and ultrastructure of the cells suggested that these T6 positive cells might be the precursors of the Langerhans cells of the skin. We have previously demonstrated by immunogold labeling techniques that the T6 surface antigen of human Langerhans cells of the skin is internalized in unfixed Langerhans cells or indeterminate cells by a process of receptor-mediated endocytosis. This process involved the formation of coated pits, coated vesicles, endosomes and lysosomes. Following this process, in Langerhans cells, gold labeled Birbeck granules appeared in the cell center often in continuity with endosomes. In the present study, we used an indirect immunogold labeling technique to reveal the T6 antigen present on the surface of living T6 positive cord blood mononuclear cells. We observed the internalization of the T6 surface antigen by a process of receptor-mediated endocytosis similar to that described in Langerhans cells of the skin. This process, however, was not followed by the appearance of intracytoplasmic Birbeck granules.

Antigens, Differentiation, T-Lymphocyte↗