The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Sem Saeland - One of the best experts on this subject based on the ideXlab platform.
-
structural studies of langerin and Birbeck granule a macromolecular organization model
Biochemistry, 2009Co-Authors: Michel Thepaut, Bertrand Arnou, Carine Monnier, Alessandra Nurisso, Sem Saeland, Corinne Vives, Richard A. Kahn, Jenny Valladeau, Christine Ebel, Colette DezutterdambuyantAbstract:Dendritic cells, a sentinel immunity cell lineage, include different cell subsets that express various C-type lectins. For example, epidermal Langerhans cells express langerin, and some dermal dendritic cells express DC-SIGN. Langerin is a crucial component of Birbeck Granules, the Langerhans cell hallmark organelle, and may have a preventive role toward HIV, by its internalization into Birbeck Granules. Since langerin carbohydrate recognition domain (CRD) is crucial for HIV interaction and Birbeck granule formation, we produced the CRD of human langerin and solved its structure at 1.5 A resolution. On this basis gp120 high-mannose oligosaccharide binding has been evaluated by molecular modeling. Hydrodynamic studies reveal a very elongated shape of recombinant langerin extracellular domain (ECD). A molecular model of the langerin ECD, integrating the CRD structure, has been generated and validated by comparison with hydrodynamic parameters. In parallel, Langerhans cells were isolated from human skin. Fro...
-
ontogeny of langerin cd207 expression in the epidermis of mice
Journal of Investigative Dermatology, 2004Co-Authors: Christoph H Tripp, Hella Stossel, Souyet Changrodriguez, Sem Saeland, Adelheid Elbeburger, Franz Koch, Patrizia Stoitzner, Patrice Douillard, Sandra Holzmann, Nikolaus RomaniAbstract:C-type lectin receptors help Langerhans cells (LC) to take up and process pathogens. Langerin/CD207 is a mannose-binding C-type lectin that is specifically expressed by LC. It is involved in antigen uptake in an as yet poorly defined way, and it is a major molecular constituent of Birbeck Granules. We studied the emergence of Langerin expression in LC in epidermal sheets and cell suspensions during ontogeny. Langerin appears later than MHC II expression. Intracellular Langerin expression becomes apparent 2–3 d after birth. Only 10 days after birth all LC co-express Langerin. The intensity of Langerin expression reaches adult levels by 3 wk after birth. Early Langerin expression appears to correlate at least in part with the physical presence of Birbeck Granules.
-
Ontogeny of Langerin/CD207 Expression in the Epidermis of Mice
Journal of Investigative Dermatology, 2004Co-Authors: Christoph H Tripp, Hella Stossel, Souyet Chang-rodriguez, Adelheid Elbe-bürger, Sem Saeland, Franz Koch, Patrizia Stoitzner, Patrice Douillard, Sandra Holzmann, Nikolaus RomaniAbstract:C-type lectin receptors help Langerhans cells (LC) to take up and process pathogens. Langerin/CD207 is a mannose-binding C-type lectin that is specifically expressed by LC. It is involved in antigen uptake in an as yet poorly defined way, and it is a major molecular constituent of Birbeck Granules. We studied the emergence of Langerin expression in LC in epidermal sheets and cell suspensions during ontogeny. Langerin appears later than MHC II expression. Intracellular Langerin expression becomes apparent 2–3 d after birth. Only 10 days after birth all LC co-express Langerin. The intensity of Langerin expression reaches adult levels by 3 wk after birth. Early Langerin expression appears to correlate at least in part with the physical presence of Birbeck Granules.
-
Langerin/CD207 sheds light on formation of Birbeck Granules and their possible function in langerhans cells
Immunologic Research, 2003Co-Authors: Jenny Valladeau, Colette Dezutter-dambuyant, Sem SaelandAbstract:Langerhans cells (LCs) are immature dendritic cells of epidermis and epithelia, playing a sentinel role through their specialized function in antigen capture, and their capacity to migrate to secondary lymphoid tissue to initiate specific immunity. A unique feature of LCs is the presence of Birbeck Granules (BGs), which are disks of two limiting membranes, separated by leaflets with periodic “zipperlike” striations. The recent identification of Lagering/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lelctin with mannose specificity expressed by LCs in epidermis and epithelia. Remarkably, transfection of Langerin cDNA into fibroblasts creates a dense network of membrane structures with features typical of BGs. Furthermore, mutated and deleted forms of Langerin have been engineered to map the functional domains essential for BG formation. Langerin is a potent LC-specific regulator of membrane superimposition and zippering, representing a key molecule to trace LCs and to probe BG function.
-
langerin cd207 sheds light on formation of Birbeck Granules and their possible function in langerhans cells
Immunologic Research, 2003Co-Authors: Jenny Valladeau, Colette Dezutterdambuyant, Sem SaelandAbstract:Langerhans cells (LCs) are immature dendritic cells of epidermis and epithelia, playing a sentinel role through their specialized function in antigen capture, and their capacity to migrate to secondary lymphoid tissue to initiate specific immunity. A unique feature of LCs is the presence of Birbeck Granules (BGs), which are disks of two limiting membranes, separated by leaflets with periodic “zipperlike” striations. The recent identification of Lagering/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lelctin with mannose specificity expressed by LCs in epidermis and epithelia. Remarkably, transfection of Langerin cDNA into fibroblasts creates a dense network of membrane structures with features typical of BGs. Furthermore, mutated and deleted forms of Langerin have been engineered to map the functional domains essential for BG formation. Langerin is a potent LC-specific regulator of membrane superimposition and zippering, representing a key molecule to trace LCs and to probe BG function.
Jenny Valladeau - One of the best experts on this subject based on the ideXlab platform.
-
structural studies of langerin and Birbeck granule a macromolecular organization model
Biochemistry, 2009Co-Authors: Michel Thepaut, Bertrand Arnou, Carine Monnier, Alessandra Nurisso, Sem Saeland, Corinne Vives, Richard A. Kahn, Jenny Valladeau, Christine Ebel, Colette DezutterdambuyantAbstract:Dendritic cells, a sentinel immunity cell lineage, include different cell subsets that express various C-type lectins. For example, epidermal Langerhans cells express langerin, and some dermal dendritic cells express DC-SIGN. Langerin is a crucial component of Birbeck Granules, the Langerhans cell hallmark organelle, and may have a preventive role toward HIV, by its internalization into Birbeck Granules. Since langerin carbohydrate recognition domain (CRD) is crucial for HIV interaction and Birbeck granule formation, we produced the CRD of human langerin and solved its structure at 1.5 A resolution. On this basis gp120 high-mannose oligosaccharide binding has been evaluated by molecular modeling. Hydrodynamic studies reveal a very elongated shape of recombinant langerin extracellular domain (ECD). A molecular model of the langerin ECD, integrating the CRD structure, has been generated and validated by comparison with hydrodynamic parameters. In parallel, Langerhans cells were isolated from human skin. Fro...
-
Langerin/CD207 sheds light on formation of Birbeck Granules and their possible function in langerhans cells
Immunologic Research, 2003Co-Authors: Jenny Valladeau, Colette Dezutter-dambuyant, Sem SaelandAbstract:Langerhans cells (LCs) are immature dendritic cells of epidermis and epithelia, playing a sentinel role through their specialized function in antigen capture, and their capacity to migrate to secondary lymphoid tissue to initiate specific immunity. A unique feature of LCs is the presence of Birbeck Granules (BGs), which are disks of two limiting membranes, separated by leaflets with periodic “zipperlike” striations. The recent identification of Lagering/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lelctin with mannose specificity expressed by LCs in epidermis and epithelia. Remarkably, transfection of Langerin cDNA into fibroblasts creates a dense network of membrane structures with features typical of BGs. Furthermore, mutated and deleted forms of Langerin have been engineered to map the functional domains essential for BG formation. Langerin is a potent LC-specific regulator of membrane superimposition and zippering, representing a key molecule to trace LCs and to probe BG function.
-
langerin cd207 sheds light on formation of Birbeck Granules and their possible function in langerhans cells
Immunologic Research, 2003Co-Authors: Jenny Valladeau, Colette Dezutterdambuyant, Sem SaelandAbstract:Langerhans cells (LCs) are immature dendritic cells of epidermis and epithelia, playing a sentinel role through their specialized function in antigen capture, and their capacity to migrate to secondary lymphoid tissue to initiate specific immunity. A unique feature of LCs is the presence of Birbeck Granules (BGs), which are disks of two limiting membranes, separated by leaflets with periodic “zipperlike” striations. The recent identification of Lagering/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lelctin with mannose specificity expressed by LCs in epidermis and epithelia. Remarkably, transfection of Langerin cDNA into fibroblasts creates a dense network of membrane structures with features typical of BGs. Furthermore, mutated and deleted forms of Langerin have been engineered to map the functional domains essential for BG formation. Langerin is a potent LC-specific regulator of membrane superimposition and zippering, representing a key molecule to trace LCs and to probe BG function.
-
Langerin, a Novel C-Type Lectin Specific to Langerhans Cells, Is an Endocytic Receptor that Induces the Formation of Birbeck Granules
Immunity, 2000Co-Authors: Jenny Valladeau, Odile Ravel, Monique Kleijmeer, Valérie Duvert-frances, Colette Dezutter-dambuyant, Kevin Moore, Claude Vincent, Daniel Schmitt, Ying Liu, Jean DavoustAbstract:We have identified a type II Ca2+-dependent lectin displaying mannose-binding specificity, exclusively expressed by Langerhans cells (LC), and named Langerin. LC are uniquely characterized by Birbeck Granules (BG), which are organelles consisting of superimposed and zippered membranes. Here, we have shown that Langerin is constitutively associated with BG and that antibody to Langerin is internalized into these structures. Remarkably, transfection of Langerin cDNA into fibroblasts created a compact network of membrane structures with typical features of BG. Langerin is thus a potent inducer of membrane superimposition and zippering leading to BG formation. Our data suggest that induction of BG is a consequence of the antigen-capture function of Langerin, allowing routing into these organelles and providing access to a nonclassical antigen-processing pathway.
Jean Salamero - One of the best experts on this subject based on the ideXlab platform.
-
rab11a controls the biogenesis of Birbeck Granules by regulating langerin recycling and stability
Molecular Biology of the Cell, 2007Co-Authors: Stephanie Uzangafsou, Jeanpierre Cazenave, Solange Monier, Huguette Bausinger, Daniel Hanau, Bruno Goud, Dan Lipsker, Fabienne Proamer, Jean SalameroAbstract:The extent to which Rab GTPases, Rab-interacting proteins, and cargo molecules cooperate in the dynamic organization of membrane architecture remains to be clarified. Langerin, a recycling protein accumulating in the Rab11-positive compartments of Langerhans cells, induces the formation of Birbeck Granules (BGs), which are membrane subdomains of the endosomal recycling network. We investigated the role of Rab11A and two members of the Rab11 family of interacting proteins, Rip11 and RCP, in Langerin traffic and the biogenesis of BGs. The overexpression of a dominant-negative Rab11A mutant or Rab11A depletion strongly influenced Langerin traffic and stability and the formation of BGs, whereas modulation of other Rab proteins involved in dynamic regulation of the endocytic-recycling pathway had no effect. Impairment of Rab11A function led to a missorting of Langerin to lysosomal compartments, but inhibition of Langerin degradation by chloroquine did not restore the formation of BGs. Loss of RCP, but not of Rip11, also had a modest, but reproducible effect on Langerin stability and BG biogenesis, pointing to a role for Rab11A-RCP complexes in these events. Our results show that Rab11A and Langerin are required for BG biogenesis, and they illustrate the role played by a Rab GTPase in the formation of a specialized subcompartment within the endocytic-recycling system.
-
Cored Tubules are Present in Human Epidermal Langerhans Cells
The Journal of investigative dermatology, 2003Co-Authors: Dan Lipsker, Umit Ziylan, Jeanpierre Cazenave, Danièle Spehner, Bruno Goud, Jean Salamero, Fabienne Proamer, Ray Mcdermott, Daniel HanauAbstract:Cored tubules are ultrastructural organelles described to date only in murine cells belonging to the Langerhans cell family and located in the dermis and its draining lymph nodes. These organelles, the function of which is unknown, differ from Birbeck Granules and are interestingly not found in murine epidermal Langerhans cells. In this work we demonstrate that cored tubules are present in freshly isolated human epidermal Langerhans cells. The tubules were found to be interconnected with structures known to belong to the early endosomal pathway and could be immunolabeled with gold-conjugated anti-CD1a and anti-Langerin monoclonal antibodies, but only at 37°C. At this temperature such antibodies are able to progress from the early sorting endosomes to the early recycling endosomes, which in human Langerhans cells include the Birbeck Granules. These findings strongly suggest that cored tubules form part of the early recycling compartment.
-
Birbeck Granules are subdomains of endosomal recycling compartment in human epidermal langerhans cells which form where langerin accumulates
Molecular Biology of the Cell, 2002Co-Authors: Ray Mc Dermott, Umit Ziylan, Jeanpierre Cazenave, Huguette Bausinger, Danièle Spehner, Bruno Goud, Dan Lipsker, Mieke A Mommaas, Graca Raposo, Jean SalameroAbstract:Birbeck Granules are unusual rod-shaped structures specific to epidermal Langerhans cells, whose origin and function remain undetermined. We investigated the intracellular location and fate of Langerin, a protein implicated in Birbeck granule biogenesis, in human epidermal Langerhans cells. In the steady state, Langerin is predominantly found in the endosomal recycling compartment and in Birbeck Granules. Langerin internalizes by classical receptor-mediated endocytosis and the first Birbeck Granules accessible to endocytosed Langerin are those connected to recycling endosomes in the pericentriolar area, where Langerin accumulates. Drug-induced inhibition of endocytosis results in the appearance of abundant open-ended Birbeck granule-like structures appended to the plasma membrane, whereas inhibition of recycling induces Birbeck Granules to merge with a tubular endosomal network. In mature Langerhans cells, Langerin traffic is abolished and the loss of internal Langerin is associated with a concomitant depletion of Birbeck Granules. Our results demonstrate an exchange of Langerin between early endosomal compartments and the plasma membrane, with dynamic retention in the endosomal recycling compartment. They show that Birbeck Granules are not endocytotic structures, rather they are subdomains of the endosomal recycling compartment that form where Langerin accumulates. Finally, our results implicate ADP-ribosylation factor proteins in Langerin trafficking and the exchange between Birbeck Granules and other endosomal membranes.
Colette Dezutterdambuyant - One of the best experts on this subject based on the ideXlab platform.
-
structural studies of langerin and Birbeck granule a macromolecular organization model
Biochemistry, 2009Co-Authors: Michel Thepaut, Bertrand Arnou, Carine Monnier, Alessandra Nurisso, Sem Saeland, Corinne Vives, Richard A. Kahn, Jenny Valladeau, Christine Ebel, Colette DezutterdambuyantAbstract:Dendritic cells, a sentinel immunity cell lineage, include different cell subsets that express various C-type lectins. For example, epidermal Langerhans cells express langerin, and some dermal dendritic cells express DC-SIGN. Langerin is a crucial component of Birbeck Granules, the Langerhans cell hallmark organelle, and may have a preventive role toward HIV, by its internalization into Birbeck Granules. Since langerin carbohydrate recognition domain (CRD) is crucial for HIV interaction and Birbeck granule formation, we produced the CRD of human langerin and solved its structure at 1.5 A resolution. On this basis gp120 high-mannose oligosaccharide binding has been evaluated by molecular modeling. Hydrodynamic studies reveal a very elongated shape of recombinant langerin extracellular domain (ECD). A molecular model of the langerin ECD, integrating the CRD structure, has been generated and validated by comparison with hydrodynamic parameters. In parallel, Langerhans cells were isolated from human skin. Fro...
-
langerin cd207 sheds light on formation of Birbeck Granules and their possible function in langerhans cells
Immunologic Research, 2003Co-Authors: Jenny Valladeau, Colette Dezutterdambuyant, Sem SaelandAbstract:Langerhans cells (LCs) are immature dendritic cells of epidermis and epithelia, playing a sentinel role through their specialized function in antigen capture, and their capacity to migrate to secondary lymphoid tissue to initiate specific immunity. A unique feature of LCs is the presence of Birbeck Granules (BGs), which are disks of two limiting membranes, separated by leaflets with periodic “zipperlike” striations. The recent identification of Lagering/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lelctin with mannose specificity expressed by LCs in epidermis and epithelia. Remarkably, transfection of Langerin cDNA into fibroblasts creates a dense network of membrane structures with features typical of BGs. Furthermore, mutated and deleted forms of Langerin have been engineered to map the functional domains essential for BG formation. Langerin is a potent LC-specific regulator of membrane superimposition and zippering, representing a key molecule to trace LCs and to probe BG function.
-
cd34 hematopoietic progenitors from human cord blood differentiate along two independent dendritic cell pathways in response to gm csf tnf alpha
Journal of Experimental Medicine, 1996Co-Authors: Christophe Caux, Colette Dezutterdambuyant, Daniel Schmitt, S. Imamura, C. Jacquet, Beatrice Vanbervliet, Catherine Massacrier, B De Saintvis, K Yoneda, J BanchereauAbstract:Human dendritic cells (DC) can now be generated in vitro in large numbers by culturing CD34+ hematopoietic progenitors in presence of GM-CSF+TNF alpha for 12 d. The present study demonstrates that cord blood CD34+ HPC indeed differentiate along two independent DC pathways. At early time points (day 5-7) during the culture, two subsets of DC precursors identified by the exclusive expression of CD1a and CD14 emerge independently. Both precursor subsets mature at day 12-14 into DC with typical morphology and phenotype (CD80, CD83, CD86, CD58, high HLA class II). CD1a+ precursors give rise to cells characterized by the expression of Birbeck Granules, the Lag antigen and E-cadherin, three markers specifically expressed on Langerhans cells in the epidermis. In contrast, the CD14+ progenitors mature into CD1a+ DC lacking Birbeck Granules, E-cadherin, and Lag antigen but expressing CD2, CD9, CD68, and the coagulation factor XIIIa described in dermal dendritic cells. The two mature DC were equally potent in stimulating allogeneic CD45RA+ naive T cells. Interestingly, the CD14+ precursors, but not the CD1a+ precursors, represent bipotent cells that can be induced to differentiate, in response to M-CSF, into macrophage-like cells, lacking accessory function for T cells. Altogether, these results demonstrate that different pathways of DC development exist: the Langerhans cells and the CD14(+)-derived DC related to dermal DC or circulating blood DC. The physiological relevance of these two pathways of DC development is discussed with regard to their potential in vivo counterparts.
Jeanpierre Cazenave - One of the best experts on this subject based on the ideXlab platform.
-
rab11a controls the biogenesis of Birbeck Granules by regulating langerin recycling and stability
Molecular Biology of the Cell, 2007Co-Authors: Stephanie Uzangafsou, Jeanpierre Cazenave, Solange Monier, Huguette Bausinger, Daniel Hanau, Bruno Goud, Dan Lipsker, Fabienne Proamer, Jean SalameroAbstract:The extent to which Rab GTPases, Rab-interacting proteins, and cargo molecules cooperate in the dynamic organization of membrane architecture remains to be clarified. Langerin, a recycling protein accumulating in the Rab11-positive compartments of Langerhans cells, induces the formation of Birbeck Granules (BGs), which are membrane subdomains of the endosomal recycling network. We investigated the role of Rab11A and two members of the Rab11 family of interacting proteins, Rip11 and RCP, in Langerin traffic and the biogenesis of BGs. The overexpression of a dominant-negative Rab11A mutant or Rab11A depletion strongly influenced Langerin traffic and stability and the formation of BGs, whereas modulation of other Rab proteins involved in dynamic regulation of the endocytic-recycling pathway had no effect. Impairment of Rab11A function led to a missorting of Langerin to lysosomal compartments, but inhibition of Langerin degradation by chloroquine did not restore the formation of BGs. Loss of RCP, but not of Rip11, also had a modest, but reproducible effect on Langerin stability and BG biogenesis, pointing to a role for Rab11A-RCP complexes in these events. Our results show that Rab11A and Langerin are required for BG biogenesis, and they illustrate the role played by a Rab GTPase in the formation of a specialized subcompartment within the endocytic-recycling system.
-
Cored Tubules are Present in Human Epidermal Langerhans Cells
The Journal of investigative dermatology, 2003Co-Authors: Dan Lipsker, Umit Ziylan, Jeanpierre Cazenave, Danièle Spehner, Bruno Goud, Jean Salamero, Fabienne Proamer, Ray Mcdermott, Daniel HanauAbstract:Cored tubules are ultrastructural organelles described to date only in murine cells belonging to the Langerhans cell family and located in the dermis and its draining lymph nodes. These organelles, the function of which is unknown, differ from Birbeck Granules and are interestingly not found in murine epidermal Langerhans cells. In this work we demonstrate that cored tubules are present in freshly isolated human epidermal Langerhans cells. The tubules were found to be interconnected with structures known to belong to the early endosomal pathway and could be immunolabeled with gold-conjugated anti-CD1a and anti-Langerin monoclonal antibodies, but only at 37°C. At this temperature such antibodies are able to progress from the early sorting endosomes to the early recycling endosomes, which in human Langerhans cells include the Birbeck Granules. These findings strongly suggest that cored tubules form part of the early recycling compartment.
-
Birbeck Granules are subdomains of endosomal recycling compartment in human epidermal langerhans cells which form where langerin accumulates
Molecular Biology of the Cell, 2002Co-Authors: Ray Mc Dermott, Umit Ziylan, Jeanpierre Cazenave, Huguette Bausinger, Danièle Spehner, Bruno Goud, Dan Lipsker, Mieke A Mommaas, Graca Raposo, Jean SalameroAbstract:Birbeck Granules are unusual rod-shaped structures specific to epidermal Langerhans cells, whose origin and function remain undetermined. We investigated the intracellular location and fate of Langerin, a protein implicated in Birbeck granule biogenesis, in human epidermal Langerhans cells. In the steady state, Langerin is predominantly found in the endosomal recycling compartment and in Birbeck Granules. Langerin internalizes by classical receptor-mediated endocytosis and the first Birbeck Granules accessible to endocytosed Langerin are those connected to recycling endosomes in the pericentriolar area, where Langerin accumulates. Drug-induced inhibition of endocytosis results in the appearance of abundant open-ended Birbeck granule-like structures appended to the plasma membrane, whereas inhibition of recycling induces Birbeck Granules to merge with a tubular endosomal network. In mature Langerhans cells, Langerin traffic is abolished and the loss of internal Langerin is associated with a concomitant depletion of Birbeck Granules. Our results demonstrate an exchange of Langerin between early endosomal compartments and the plasma membrane, with dynamic retention in the endosomal recycling compartment. They show that Birbeck Granules are not endocytotic structures, rather they are subdomains of the endosomal recycling compartment that form where Langerin accumulates. Finally, our results implicate ADP-ribosylation factor proteins in Langerin trafficking and the exchange between Birbeck Granules and other endosomal membranes.
-
Ultrastructural similarities between epidermal Langerhans cell Birbeck Granules and the surface-connected canalicular system of EDTA-treated human blood platelets.
The Journal of investigative dermatology, 1991Co-Authors: Daniel Hanau, Didier A Schmitt, Michel Fabre, Christian Gachet, Philippe Ohlmann, Christine Brisson, Jeanpierre CazenaveAbstract:Abstract 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 β3 integrin subfamily (αIIbβ3) 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.