Demonstration of the Langerhans granule by lanthanum

Langerhans Cell Granule as Phagocytic Organelle

In recent years the epidermal Langerhans cell has been considered to belong to histiocytic rather than melanocytic lineage. However, the functional significance of the Langerhans cell granule, which has also been called Bribeck's granule or racket body, has not been settled. In this study, 0.1 ml of horseradish peroxidase solution (25 mg in 1.0 ml normal saline) was injected intradermally into six sites on the back of a normal adult guinea pig. The injected sites were biopsied at 10, 30, 60, 120, 180 and 300 minutes and later at 22, 120 and 142 hours. The epidermis was minced with sharp razor blades into 1 mm blocks and fixed in 5% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.2) for 3 hours at 4°C. After overnight rinse in the same buffer, tissue blocks were minced again into smaller pieces to facilitate the penetration of benzidine and hydrogen peroxide. Benzidine reaction was done according to the method of Schneeberger-Keeley and Karnowsky.

Lanthanum-Induced Gastrointestinal Histiocytosis

A patient with end-stage renal disease (ESRD) on hemodialysis presented with fever, anorexia, and nausea shortly after starting oral lanthanum carbonate for phosphate control. Gastric and duodenal biopsies demonstrated diffuse histiocytosis with intracellular aggregates of basophilic foreign material. Transmission electron microscopy, an underutilized diagnostic test, revealed the nature of the aggregates as heavy metal particles, consistent with lanthanum. Symptoms and histiocytosis improved after discontinuation of lanthanum. Lanthanum may be an underdiagnosed cause of gastrointestinal histiocytosis.

Langerin/CD207 sheds light on formation of birbeck granules and their possible function in Langerhans cells

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 Langerin/CD207 has allowed researchers to decipher the mechanism of BG formation and approach an understanding of their function. Langerin is a type II lectin 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.

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.

Histiocytes X and X body reactivity with concanavalin A, peanut agglutinin and BSPT

The ultrastructural and histochemical exploration of histiocytes X done by the means of Concanavalin A (Con A), peanut agglutinin (PNA) and BSPT demonstrate that the plasma membrane of histiocytes X shared some properties with all the other cells and is also specialized. The rod part of the X body has the same properties as the plasma membrane while its vesicular part differs and is closer to the inner membrane system of the cell. In consequence it is suggested that the rod part of the X body is a specialized pathway or shuttle for receptor linked glycoprotein exchanges in highly specialized cells.

The Langerhans cell granule is an adsorptive endocytic organelle

The role of Langerhans cell granules (LCG) in adsorptive endocytosis was studied by using concanavalin A (Con A) and heterologous anti-epidermal cell serum (AES) as ligands. Isolated epidermal cells were obtained by trypsinization of guinea pig skin fragments and exposed to ferritin-conjugated Con A or AES followed by ferritin-conjugated second antibody at 37 degrees C for various times up to 30 min. Langerhans cells among the treated epidermal cells were observed by electron microscopy. Shortly after the incubation, a few LCG in the cell periphery were filled with ferritin particles in the bulb portion. After prolonged incubation, ferritin-containing LCG increased in number and seemed to move to the juxtanuclear area. The granules were derived from plasma membrane invaginations that collected ferritin particles in a saclike extension at the end. Some of these invaginations were apparently of coated pit origin. The contents in the bulb of LCG seemed to be delivered finally to intracellular degradation compartments. Our findings clearly demonstrate that LCG are an adsorptive endocytic organelle.

Coated Langerhans cell granules in histiocytosis X cells

Histiocytosis X cells (HXC) and epidermal Langerhans cells (LC) are thought to be closely related because they share morphologic features and immunologic markers. One of these common markers, the LC granule, is an acknowledged morphologic criterion for the identification of these cell types, but its function and, thus, significance are as yet unknown. In this study, we report the presence of a fuzzy coat radiating from the cytoplasmic face of the LC granule membrane in HXC. This bristly coat is indistinguishable from that of coated vesicles and pits and, thus, represents a strong morphologic clue to the function of LC granules because coated structures have been shown to be involved in the selective transport of molecules in eukaryotic cells.

An ultrastructural and immunohistochemical study on mandibular lesion of Letterer-Siwe disease

A mandibular lesion from an infant with Letterer-Siwe disease was studied by electron microscopy and immunohistochemistry. Ultrastructurally, two types of cells were identified; clear and dark cells. Clear cells had indented nuclei and langerhans cell granules, while dark cells were characterized by the occasional presence of a large number of lysosomes. Lysozyme was usually not detectable in proliferating cells with indented nuclei, but it was strongly positive in cells without indented nuclei. The latter also usually contained IgG, although the occurrence of cytoplasmic IgM, A, D and E seemed to be negative in both types of cells. Thus clear cells showed a close resemblance to Langerhans cells and dark cells had features of ordinary histiocytes. Although the intimate relationship between these two types of cells remains obscure, our findings suggest that Letterer-Siwe disease may be a reactive or tumorous condition of a cellular subpopulation of Langerhans cells with a proliferation of differentiated histiocytes.

Dense bodies and Langerhans granules after application of podophyllum resin

The application of an alcoholic solution of podophyllum resin at concentrations above 10% for seven hours on guinea-pig udders increases the number of dense intracytoplasmic bodies in the Langerhans cells localized in the epidermis. A close relationship can be established between these inclusions and the typical Langerhans granules in view of the numerous intermediate forms with features of one or the other. Serial sections of these structures confirm the irregularity not only of the lysosome-like bodies but also of the Langerhans granules, which may be fusiform or oblong or even present two vesicular dilatations, one at each end of the rod.

Intracytoplasmic junctions in cardiac muscle cells

JUNCTIONAL STRUCTURES FORMED BY TWO PARTS OF THE PLASMA MEMBRANE OF THE SAME CARDIAC MUSCLE CELL WERE OBSERVED IN VENTRICULAR MYOCARDIUM OF: a) patients with neoplasms, aortic valvular disease or idiopathic hypertrophic subaortic stenosis and b) dogs subjected to prolonged normothermic anoxic cardiac arrest. Most of these structures had features of desmosomes; other, more complex structures had components with features of desmosomes, fasciae adherentes and nexuses, and, therefore, resembled intercalated discs. These intracytoplasmic junctions were localized to: a) the peripheral cytoplasm at the sides or ends of cells, b) narrow invaginations of plasma membranes, c) narrow zones of deep, broad plasmalemmal invaginations and d) narrow branches of T tubules. In patients with idiopathic hypertrophic subaortic stenosis or aortic valvular disease and in the dogs subjected to anoxic cardiac arrest, intracytoplasmic junctions were observed in hypertrophied or degenerated muscle cells which were located in areas of fibrosis and which showed loss of contact with adjacent cells. In patients with neoplasms, intracyto-plasmic junctions were found in degenerated cells which were located in areas of interstitial edema and which also showed loss of contact with adjacent cells. Our observations suggest that remodeling of cell surfaces following loss of intercellular contact is the most likely mechanism of formation of intracytoplasmic junctions.