Langerhans cells can express neuron-specific enolase immunoreactivity

Arch Dermatol Res (1991) 283:10-12

Archives of

N@$@SJ@B 9 Springer-Verlag 1991

Langerhans cells can express neuron-specific enolase immunoreactivity F. Fantini 1, C. Pincelli l, C. Sevignani 1 A. Baraldi 2, and A. Giannetti ~ 1 Institute of Dermatology, University of Modena, Via del Pozzo, 71, Modena, 1-41100 2 Institute of Nephrology, University of Modena, Modena, Italy Received July 31, 1990

Key words: Neuron-specific enolase cells - Immunohistochemistry

Langerhans

Enolases (2-phospho-D-glycerate hydrolase) are glycolytic cytoplasmic enzymes, with multiple isoenzymes, widely distributed in mammalian tissues. Enolase isoenzymes are dimers composed of three immunologically distinct subunits (c~,/3, 7). The isoenzymes containing the 7-subunit were initially found in neuronal and neuroendocrine cells [12] and tumours [14, 15], and subsequently considered to be neuron specific. The presence of 7-isoenzymes was later also demonstrated in a wide variety of other tissue, both normal [4] and malignant [9]. Recently, neuron-specific enolase (NSE) immunocytochemical positivity was observed in a few lymph nodal neoplastic cells in two out of 12 patients affected by disseminated histiocytosis X [8]. Here we report immunohistochemical evidence of NSE immunoreactivity (IR) in normal human epidermal Langerhans cells. Skin specimens were taken from various regions of normal human skin (scalp, arm, face, fingertip, prepuce, lower limb). Samples were taken under local anaesthesia either as punch biopsies from adult volunteers or as margins of surgical ablations. Most specimens were immersion-fixed in picric acid/formalin, then frozen in liquid nitrogen and stored at - 8 0 ~ until used. A few specimens were fixed in formalin and embedded in paraffin. Both procedures have been demonstrated to be suitable for NSE immunostaining [1]. Sections ( 4 - 1 4 gm) from a total of 37 specimens taken from 32 healthy subjects were processed with a biotin-streptavidin-fluorescein technique. A few sections were stained using the avidin-biotin-peroxidase method. Two rabbit polyclonal antisera, raised against the 7/Y enolase isoenzyme (purchased from Incstar Corp., Offprint requests to: F. Fantini

Stillwater, Minn, USA, and Dakopatts a/s, Copenhagen, Denmark) were used as primary antisera. Negative controls were performed by replacing the primary antiserum with rabbit non-immune serum. NSE IR was detected both in nerve bundles and fibres in all sections examined, with an IR pattern similar to that previously described [2]. A cytoplasmic staining was seen in many cells of the secretory portions of the eccrine sweat glands and in dendritic cellular elements of the basal epidermis, as previously reported [3]. In 15 out of 37 samples a cytoplasmic staining was observed in a few dendritic cells in a suprabasal position in both the epidermis and the follicular epithelium (Fig. 1). The intensity of IR varied between the different samples. Using the immunoperoxidase method, positive staining was expressed as granular cytoplasmic reactivity (Fig. 2). A double immunofluorescence labelling technique was then used in order to confirm the nature of these NSE-reactive intraepidermal dendritic cells. Some specimens were first stained with a biotin-avidin-rhodamine technique for NSE. After washing, a fluorescein isothiocyanate-conjugated anti-T6 monoclonal antibody (Ortho Pharmaceutical Corp., Raritan, NJ, USA) was applied. All NSE-positive suprabasal dendritic cells were found to express T6 antigen, although the number of NSE IR cells was considerably lower than the total number of T6-positive epidermal cells. No labelling was seen in negative controls. These findings indicate that 7-enolase IR may also be expressed in normal human epidermal Langerhans cells. NSE was initially assumed to be a specific marker for neuronal cells and tumours. Several subsequent immunocytochemical [4], enzymatic [5, 9] and radioimmunological [9] studies demonstrated that the 7subunit containing isoenzymes can be found in several non-neuronal normal and neoplastic tissues. Moreover, 7-subunit expression has been shown in established cell lines free of any contaminating nervous tissue [9]. Interestingly, 7-enolase has also been demonstrated in some normal (platelets, megakaryocytes, erythrocytes, plasma

F. Fantini et al. : Neuron-specific enolase and Langerhans cells

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Fig. 1. Immunofluorescence staining of NSE IR LC (arrows) and NSE IR intraepidermal nerve endings (arrowheads). x 400

Fig. 2. Immunoperoxidase staining ofNSE IR LC (arrows). NSE IR cells are also present in the basal epidermis (arrowheads). x 400

ceils, lymphocytes) [4, 5] and neoplastic (malignant lymphomas, histiocytosis X) [7, 8, 15] bone-marrow-derived cells. The regulation and functional significance of the expression of the 7-subunit gene in nervous and non-nervous cells are not fully understood. It has been hypothesized that the 7-form is associated with a greater stability, since the 7/7 isoenzyme is more resistant to chloride and heat-induced denaturation [6]. An increased metabolic demand may be another factor in the 7-expression [11]. In the nervous system, this expression seems to be closely associated with neuronal differentiation. Indeed, during fetal development of the nervous system,

neurons switch from the ~ to the 7-form of enolase [13]. The presence of 7-enolase in lymphocytes is suggested to be related to a particular differentiation stage, possibly to activation, as indicated by the appearance of the c~/7form after phytohaemagglutinin stimulation [10]. Whether the presence of the IR 7-enolase subunit in a minority of normal Langerhans cells might have a similar significance remains to be established. Our results confirm that NS E cannot be considered an exclusive marker of nervous structures, and its expression could possibly be correlated to particular metabolic conditions.

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