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Biomedical subjects

D Hanau

Publications and source records attributed to D Hanau.

At least 19 recordsLinked to original sources
PubMed1995

Activation of human epidermal Langerhans cells by engagement of the high affinity receptor for IgE, Fc epsilon RI.

Human epidermal Langerhans cells (LCs) bind IgE via the high affinity receptor (Fc epsilon RI), and therefore are suspected to be involved in the genesis of atopic diseases. In this study, we report that surface expression of Fc epsilon RI is increased dramatically on LCs from patients with atopic dermatitis (AD) when compared with nonatopic individuals. Cross-linking of Fc epsilon RI on LCs from nonatopic individuals and patients with AD leads to a rapid tyrosine phosphorylation of several proteins, including p72, p77, and p95. However, upon receptor ligation, calcium mobilization is only detected in LCs freshly isolated from patients with AD (responder LCs), but not in those from normal skin of healthy individuals (nonresponder LCs). The beta-chain of Fc epsilon RI is not detected in normal LCs and only in a minority of LCs from atopic individuals, indicating that it is not related to the capacity of LCs to respond to Fc epsilon RI-mediated activation. In contrast, LCs from both nonatopic and atopic individuals internalize Fc epsilon RI by receptor-mediated endocytosis as a prerequisite for Ag focusing. Therefore, LCs from normal individuals and individuals with AD differ functionally by their Fc epsilon RI expression and by a distinct ability to respond to Fc epsilon RI-mediated activation.

Antibodies, Monoclonal↗
PubMed1995

Role of B cell receptor Ig alpha and Ig beta subunits in MHC class II-restricted antigen presentation.

The ability of the B cell antigen receptors (BCRs) to enhance MHC class II-restricted antigen presentation was ascribed to mig-associated Ig alpha/Ig beta heterodimers. The relative role of Ig alpha and Ig beta subunits in antigen presentation was investigated by fusing their cytoplasmic tails to the extracellular and transmembrane domains of Fc receptors. Ig alpha and Ig beta chimera mediate antigen internalization and increase the efficiency of antigen presentation, but they drive antigens to different endosomal compartments. Furthermore, antigens internalized by either chimera are degraded and presented with different kinetics. The cytoplasmic tail of Ig alpha targets antigen towards a major population of newly synthesized MHC class II located in class II-rich compartments. In contrast, Ig beta targets antigen towards a minor population of recycling MHC class II molecules, located in transferrin receptor-containing endosomes. Altogether, our data indicate that the composition of BCR could be therefore an important way to modulate the immune response.

Animals↗
PubMed1994

Homozygous human TAP peptide transporter mutation in HLA class I deficiency.

Human lymphocyte antigen (HLA) class I proteins of the major histocompatibility complex are largely dependent for expression on small peptides supplied to them by transporter associated with antigen processing (TAP) protein. An inherited human deficiency in the TAP transporter was identified in two siblings suffering from recurrent respiratory bacterial infections. The expression on the cell surface of class I proteins was very low, whereas that of CD1a was normal, and the cytotoxicity of natural killer cells was affected. In addition, CD8+ alpha beta T cells were present in low but significant numbers and were cytotoxic in the most severely affected sibling, who also showed an increase in CD4+CD8+ T cells and gamma delta T cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

CD1 expression is not affected by human peptide transporter deficiency.

Conventional major histocompatibility complex class I molecules are highly polymorphic and present peptides to cytotoxic T cells. These peptides derive from the proteolytic degradation of endogenous proteins in the cytosol and are translocated into the endoplasmic reticulum by a peptide transporter consisting of two transporter associated with antigen processing (TAP) molecules. Absence of this transporter leads to the synthesis of unstable peptide free class I molecules that are weakly expressed on the cell surface. Mouse nonconventional class I molecules (class Ib) may also present TAP-dependent peptides. In humans, CD1 antigens are nonconventional class I molecules. Recently, we characterized a human HLA class I deficiency resulting from a homozygous TAP deficiency. We show here that CD1a and -c are normally expressed on epidermal Langerhans cells of the TAP-deficient patients, as are CD1a, -b, and -c on dendritic cells differentiated in vitro from monocytes. Moreover, the CD1a antigens present on the surface of the dendritic cells are functional, since they internalize by receptor-mediated endocytosis gold-labeled F(ab')2 fragments of an anti-CD1a mAb. This suggests either that CD1 molecules are empty molecules, that they are more stable than empty conventional class I proteins, or that CD1 molecules present TAP-independent peptides.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Antibodies to thrombomodulin induce receptor-mediated endocytosis in human saphenous vein endothelial cells.

The membrane glycoprotein thrombomodulin (TM) is an essential endothelial cell (EC) cofactor, which forms a 1:1 stoichiometric complex with thrombin. Binding of thrombin to the high affinity TM receptor transforms its procoagulant activity into an anticoagulant potential, by activating protein C. The fate of TM in the presence of thrombin is still unclear: some authors claim that the thrombin-TM complex is internalized in EC, while others find this complex to be stable for at least 2 h at 37 degrees C on the EC surface. In the present study, we investigated the interactions of thrombin and Fab-fragments of anti-TM antibodies, coupled to 5 or 15 nm gold particles with saphenous vein endothelial cells. Our results demonstrate that TM can be observed both on the plasma membrane and in coated structures only in the presence of anti-TM antibodies. Addition of thrombin decreased the extent of this labeling, while in double labeling experiments, where cells were incubated with 5 nm gold coupled thrombin and 15 nm gold coupled Fab fragments of anti-TM antibodies, thrombin was cointernalized only when anti-TM antibodies were present. These results show that thrombin-TM complex is not significantly internalized in EC. The internalization of this complex induced by anti-TM antibodies could play an important role in the thrombotic complications induced by anti-EC autoantibodies.

Amino Acid Sequence↗
PubMed1992

Human epidermal Langerhans cells express the high affinity receptor for immunoglobulin E (Fc epsilon RI).

It has been suggested that epidermal Langerhans cells (LC) bearing immunoglobulin E (IgE) may be involved in the genesis of atopic disease. The identity of the IgE receptor(s) on LC remained unclear, although it represents a crucial point in understanding cellular events linked to the binding of allergens to LC via IgE. In this report, we demonstrate that epidermal LC express the high affinity receptor for the Fc fragment of IgE (Fc epsilon RI) which has, so far, only been described on mast cells and basophils. Epidermal LC react with antibodies specific for the alpha subunit of the tetrameric (alpha, beta, 2 gamma) Fc epsilon RI. Specific transcripts for Fc epsilon RI alpha and Fc epsilon RI gamma were detected in LC and correspond to those of human basophils and of the human basophil cell line KU812. Furthermore, human basophils, KU812 cells, and LC express the putative beta subunit. Thus human LC express the complete structure of Fc epsilon RI. This finding opens new perspectives in the putative functional role of this structure on antigen-presenting cells.

Amino Acid Sequence↗
PubMed1992

Fc gamma RII/CD32-negative human Langerhans cells may be responsible for the immunostimulatory activity of freshly isolated epidermal cells.

Cultured murine and human epidermal Langerhans cells (LC) undergo a phenotypical and functional maturation process. In fact, they loose Fc gamma RII and Birbeck granules, increase HLA-DR expression, and become potent accessory cells for allogeneic MLR. However, resident/freshly isolated human epidermal LC represent a phenotypically heterogeneous cell population. Indeed, a subset of CD1a+ LC lacks Birbeck granules, is Fc gamma RII/CD32-, and strongly expresses HLA-DR and the RFD1 antigen that is considered to be specific for interdigitating cells. In the present study the functional capacity of this Fc gamma RII/CD32- CD1a+ LC subset was investigated in MLR assays by comparing the stimulatory activity of freshly isolated crude epidermal cells (EC) with that of freshly isolated EC depleted in CD1a+ or in Fc gamma RII+ cells. Thereby, we observed that crude EC stimulated allogeneic PBMC while the removal of CD1a+ cells abrogated this stimulation. However, crude EC depleted in Fc gamma RII/CD32+ cells still exhibited a stimulatory capacity that was at least equal to that of crude EC. Taken together, these data suggest that among resident human epidermal LC there exists a subset of phenotypically and functionally more differentiated cells that may be solely responsible for the stimulatory capacity of freshly isolated crude EC.

Antibodies, Monoclonal↗
PubMed1992

Alpha IIB beta 3 integrin dissociation induced by EDTA results in formation of Birbeck granule-like structures in human blood platelets.

EDTA (5 mM at 37 degrees C and pH 7.4 for 30 min) induces morphologic changes in the platelet surface-connected canalicular system (SCCS), in particular the collapse of some portions of the canaliculi. These collapsed elements are made up of two parallel limiting membranes and a central irregular striated zone, a pentalaminar organization that clearly resembles that of Langerhans cell Birbeck granules (BG). Such BG-like structures are also seen between adjacent platelets in EDTA-treated platelet microaggregates. EDTA is known to induce an irreversible dissociation of the platelet membrane glycoprotein(GP)IIb-IIIa, the alpha IIb beta 3 platelet-specific intergrin, a calcium-dependent heterodimer that serves as an inducible receptor for fibrinogen and is essential for platelet aggregation. Hence, we looked for involvement of the GPIIb-IIIa in the formation of these BG-like modifications. We observed that these changes i) cannot be induced in type I Glanzmann's thrombasthenia, where the GPIIb-IIIa complexes are absent; ii) did not appear when human platelets were pre-incubated with MoAb anti-GPIIb-IIIa complex, which protected GPIIb-IIIa from EDTA-induced dissociation; iii) appeared only at alkaline pH and 37 degrees C, which corresponds to the range of pH and temperature where EDTA can dissociate the GPIIb-IIIa complexes; iv) are accompanied by the dissappearance on fluorescence flow cytometry analysis of the heterodimer specific epitopes; and v) do not appear in rat platelets at pH 7.4 where GPIIb-IIIa does not dissociate after EDTA treatment. Thus, the appearance of BG-like structures in the platelet SCCS is directly dependent on the EDTA-induced dissociation of the GPIIb-IIIa complexes. Furthermore, using gold-labeled MoAb concomitantly with the addition of EDTA, we observed that only GPIIb is present in the collapsed portions of the canaliculi. On Lowicryl thin sections essentially polyclonal antibodies to GPIIb labeled the central striated zone. All these observations lead us to suggest that homopolymers of GPIIb could be responsible for "zipping" of the SCCS and raise the question of the participation of a Langerhans cell integrin in the formation of Langerhans cell BG.

Blood Platelets↗
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↗