G. De Panfilis

Primary cutaneous plasmacytoma: a role for a triggering stimulus?

Primary cutaneous plasmacytoma is a rare type of cutaneous B‐cell lymphoma, characterized by clonal proliferation of plasma cells, that primarily develops in the skin. Five cases have been described to date in which a local triggering stimulus may be involved in development of this skin tumour. We describe the case of a primary cutaneous plasmacytoma localized to the lower lip. This site had been affected for 15 years with recurrent herpes simplex virus‐1 infection. Neoplastic plasma cells were found to be bcl‐2‐positive. We hypothesize that chronic stimulation of keratinocytes by herpes simplex virus‐1, possibly through toll‐like receptors, may have favoured the release of cytokines (e.g. interleukin‐6) able to induce plasma cell proliferation, transformation and survival.

Hydrogen sulfide inhibits IL-8 expression in human keratinocytes via MAP kinase signaling

Sulfur is able to penetrate the skin, and a sulfur-rich balneotherapy has been suggested to be effective in the treatment of psoriasis. Psoriasis is now considered a genetically programmed, immune-mediated, inflammatory disease, in which intralesional T lymphocytes trigger keratinocytes to proliferate and perpetuate the disease process. Interleukin (IL)-17 and IL-22 produced by Th1/Th17 lymphocytes induce IL-8 secretion by keratinocytes, a key event in the pathogenesis of the disease. It is now clear that mitogen-activated protein kinase (MAPK) (extracellular signal-regulated kinases (ERK) 1 and 2) activity is required for IL-17-induced IL-8 synthesis by keratinocytes, and, in fact, MAPK activity is increased in lesional psoriatic skin. Here, we demonstrate both in vitro and in vivo on primary psoriatic lesions that pharmacological inhibitors of ERKs as well as hydrogen sulfide not only reduce the basal expression and secretion of IL-8, but also interfere with IL-17- and IL-22-induced IL-8 production. These observations, together with the known anti-inflammatory activity of H2S, are relevant to understanding some previously unexplained biological effects exerted by sulfur therapy.

Immunoperoxidase-immunogold double labelling in immunoelectronmicroscopy of large granular lymphocytes

A method for better characterization of mononuclear cell subpopulations using detection of 2 surface antigens simultaneously in electron microscopy was developed with immunoperoxidase-immunogold double labelling. Monoclonal antibodies of IgG and IgM classes were used in the first step, and colloidal gold-labelled anti-mouse IgG antibody and peroxidase-labelled anti-mouse IgM antibody (mu chain-specific) in the second step. Immunoelectronmicroscopy with such double labelling improves ultrastructural analysis of mononuclear cell subpopulations.

Immunoelectron microscopic characterization of a subpopulation of freshly isolated epidermal Langerhans cells that reacts with anti-CD23 monoclonal antibody

Large subsets of leucocytes were recently shown to express the low affinity receptor for the Fc portion of IgE. Because Langerhans cells (LC) are epidermal leucocytes, we investigated whether LC of normal human subjects might express this receptor. Whereas conventional immunofluorescence on epidermal sheets gave negative results, highly sensitive immunoelectron microscopy revealed that a subset (about one‐third) of freshly isolated LC express the CD23 molecule.

Keratinocytes constitutively express the CD95 ligand molecule on the plasma membrane: an in situ immunoelectron microscopy study on ultracryosections of normal human skin

Background Tissue homeostasis is mainly preserved by cytolytic functions. Cytolytic cells, when expressing the CD95 ligand (Fas‐L) molecule on the cell membrane, are able to kill CD95 (Fas)‐expressing target cells. Although cultured epidermal keratinocytes (KC) have been shown to express Fas‐L, and normal skin has been shown to bear Fas‐L mRNA, efforts so far to find possible constitutive Fas‐L expression on the cell membrane by resting KC in normal human epidermis (i.e. in a functionally active location) have been inconclusive.

The fine structure of HNK-1 (Leu7) positive cells

SummaryThe ultrastructural characteristics of HNK-1 (Leu7) positive cells, visualized with a peroxidase labelled anti-mouse IgM serum, were analysed. Our investigation demonstrates: 1) the majority of Leu7 positive cells has a low nuclear/cytoplasmic ratio (N/C), an irregular outline, a well developed smooth endoplasmic reticulum, parallel tubular arrays (PTA) and electron dense granules; 2) the minority of Leu7 positive cells has a high N/C, regular profiles and lacks electron dense granules. The presence of two distinct ultrastructural patterns within Leu7 positive cells may represent: 1) the expression of subsequent stages of cell differentiation; 2) two distinct Leu7 positive cell subpopulations.

Keratinocytes resident in normal human skin constitutively express, at low levels, the intercellular adhesion molecule-1. An in situ immunoelectronmicroscopy study

Summary The expression of intercellular adhesion molecule‐1 (ICAM‐1) on keratinocytes (KC) was previously demonstrated in biopsies from various inflammatory skin lesions. KC were, however, found virtually ICAM‐1 negative, in normal skin, when the same immunocytochemical techniques were employed. By contrast, epithelial cells resident in different organs constitutively express ICAM‐1, albeit weakly. The aim of the present study was to use an immunostaining system more sensitive than the conventional immunocytochemistry, namely the in situ immunogold labelling of ultracryosections, to investigate the constitutive ICAM‐1 expression by resting KC in normal skin, in vivo. The semiquantitative analysis performed on 500 resident KC, visualized within tissue ultracryosections of normal human skin, revealed that gold granules were present along the cell membrane in a small percentage (14·6%) of resident KC. The density of gold particles (10 nm sized) observed on the cell surface per KC section was as scarce as 13·72 ± 4·6 (mean ± standard deviation), although highly significant when compared with controls (P < 0·005). This indicates the presumably low expression of ICAM‐1 moieties on the plasma membrane of this KC subset. This ICAM‐1 expression could be important in modulating the trafficking to and from normal epidermis of migrating Langerhans cells and occasional leucocytes. The fact that the ICAM‐1 expression on KC in normal skin is limited can be considered favourable, because it can account for the prevention of inappropriate KC/leucocyte interactions in the resting cutaneous environment.

Cytoplasmic β-catenin is lacking in a subset of melanoma-associated naevi, but is detectable in naevus-associated melanomas: potential implications for melanoma tumorigenesis?

Summary Background  An excess of intracellular β‐catenin protein is triggered by various genetic alterations in melanoma cell lines, and has been suggested to play a role in melanoma tumorigenesis.

Alterations in molecular killing mechanisms: implications in skin disease

Cytolytic T lymphocytes exert two main specific molecular killing mechanisms against target cells, namely (i) they can synthesize and release soluble cytolytic factors, and (ii) they can express effector molecules that act as ligands of receptors expressed by target cells on the cell surface; by these two pathways cytolytic T lymphocytes kill several targets, e.g. cells infected with intracellular pathogens, cells transformed by malignancy and cells producing autoantibodies. This review investigates the contribution from alterations in these molecular killing mechanisms to the pathogenesis of cutaneous diseases. In fact, molecular components involved in such killing mechanisms are often altered or distorted in skin pathology, e.g. cutaneous viral infections, skin cancer, contact hypersensitivity and autoimmune diseases with cutaneous involvement. Treatments capable of repairing the molecular components operating in such killing mechanisms could presumably favour the resolution of these skin diseases.

Dexamethasone-induced healing of chronic leg ulcers in a patient with defective organization of the extracellular matrix of fibronectin.

Previous investigations have shown that skin fibroblasts derived from patients affected by Ehlers–Danlos syndrome (EDS) lack an organized extracellular matrix (ECM) of fibronectin (FN). As retarded wound healing is a sign of EDS, we hypothesized that a young healthy man suffering from chronic recalcitrant leg ulcers might be affected by a defect of FN–ECM organization similar to that observed in EDS. Immunofluorescence of cultured skin fibroblasts obtained from skin biopsies from the patient and a control demonstrated that the patient’s fibroblasts lacked FN–ECM organization, in contrast with those of the control; this was restored by 10−7 mol/L dexamethasone (DEX) in vitro. DEX treatment of the patient was associated with healing of his leg ulcers. In conclusion, DEX may be effective in reversing impaired wound healing associated with a lack of FN–ECM organization