Giorgio Pasolini

A reassessment of diagnostic criteria and treatment of idiopathic urticarial vasculitis: a retrospective study of 47 patients.

Background.  Urticarial vasculitis (UV) is an uncommon type of chronic urticaria (CU), which exhibits leucocytoclastic vasculitis. Painful and long‐lasting (> 24 h) weals associated with purpura or bruising are considered indicative of UV. It is often responsive to oral corticosteroids and poorly to oral antihistamines. Hypocomplementaemia and systemic involvement are also commonly reported.

Identification of Fas-L-Expressing Apoptotic T Lymphocytes in Normal Human Peripheral Blood: In Vivo Suicide

Fas-L molecules expressed by in vitro stimulated T cells may be critically involved in suicidal activation-induced cell death (AICD) of such cells through engagement of their Fas receptors. A similar suicide of T cells was postulated to occur even in vivo, to eliminate dangerous activated lymphocytes; however, the demonstration of suicidal AICD of T cells in healthy humans in vivo is still lacking. We therefore investigated the possible occurrence of Fas-L-linked suicidal apoptosis of T cells in normal human peripheral blood. For this purpose, we took advantage of immunoelectron microscopy, which allows simultaneous visualization of the morphological apoptotic cellular changes together with surface expression of Fas-L molecules. Very few T lymphocytes were observed showing the ultrastructural features of apoptotic lymphocytes; these occasional apoptotic T cells, together with the majority of the normal T cell population, expressed the Fas molecule on the plasma membrane, as expected. Interestingly, the apoptotic cells were also Fas-L-positive, whereas normal T cells were Fas-L-negative. Such Fas-L-associated T cell suicide operating in vivo in healthy individuals is presumably able to suppress immune responses and prevent autoreactivity, thus maintaining the homeostasis of human blood.

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.

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.

Melanocytes freshly isolated from normal human skin express the cell membrane receptor for the adhesive glycoprotein thrombospondin

Summary Thrombospondin (TSP) is an adhesive protein with multiple binding sites, which Is able to mediate several cell‐to‐cell and cell‐to‐matrix interactions, particularly through its cell membrane receptor (TSP‐R). Because human keratinocytes are able to synthesize and express TSP, and as TSP is also localized at the dermal–epidermal junction in normal human skin, we questioned whether epidermal cells are able to bind available TSP, that is to express TSP‐R. To investigate this, we employed gold immunoelectron microscopy on epidermal cells freshly isolated from normal human skin; the TSP‐R was detected by OKM5 monoclonal antibody. Epidermal cells showing ultrastructural characteristics of melanocytes were gold‐stained on their plasma membrane, whereas keratinocytes. Langerhans cells and lymphocytes were unstained. Although functional studies are clearly necessary to clarify the role(s) played by the TSP‐R on the cell surface of melanocytes, it is tempting to speculate that the TSP‐R may be important for melanocyte adhesion to the dermal–epidermal junction and to keratinocytes. Such adhesion may not only subserve the steric localization of melanocytes. hut also have important implications for those functional activities of melanocytes which have been shown to require close contact between these cells and adjacent keratinocytes and/or basement membrane components.

Allergic contact dermatitis from nickel in a piezoelectrical device for mosquito bites (‘Click®’)

The patient is a 32-year-old woman, with a 2-day history of an intensely itching dermatitis of the right ankle. 3 days before, a mosquito’s bite had caused the sudden appearance of an erythematous and edematous plaque. In the attempt to reduce the inflammation and to relief the itch, she repeatedly applied a piezoelectrical medical device called ‘Click ’ (Tecnimed srl, Vedano Olona-Varese, Italy) (Fig. 1) on the skin lesion. After a few hours, erythema and oedema enhanced, vesicles developed and itching became worse and worse while she increased the frequency of applications, thinking to a natural course of the insect bite reaction. At dermatological examination, a roundish, 10 cm in diameter, inflammatory plaque with severe erythema, oedema, and vesiculation was seen on the right ankle. Twice daily application of a mild corticosteroid cream allowed the complete healing of the skin lesion within a week. Patch testing with the ‘standard series’ (F.I.R.M.A., Florence, Italy) according to SIDAPA (Società Italiana di Dermatologia Allergologica Professionale e Ambientale) guidelines (1) elicited a strong positive reaction (þþþ) to nickel. Fragments of the plastic and metallic parts of the scaffold of ‘Click ’ were applied separately on the volar surface of the forearm and only the metallic parts elicited an intensely (þþþ) positive reaction. Afterwards, the company Tecnimed srl declared that this part was made with nickelated brass.