C-type lectins are cell surface receptors that recognize carbohydrate structures which are often part of microbial pathogens. Several of these molecules are expressed on dendritic cells and are involved in antigen uptake. Expression of C-type lectins on dendritic cells of the human skin, i.e. Langerhans cells of the epidermis and dermal dendritic cells, has been incompletely studied to date. We therefore investigated C-type lectins in situ and on dendritic cells obtained by migration from skin explants by immunofluorescence and flow cytometry. Emphasis was laid on expression patterns of DEC-205/CD205 and BDCA-2, a marker for plasmacytoid dendritic cells. Langerhans cells in situ expressed low levels of DEC-205. Expression was upregulated upon maturation in skin explant organ culture. Most dermal dendritic cells were found to be positive for DEC-205 and DC-SIGN/CD209. Few BDCA-2-expressing cells were found in most skin samples. They were located in small groups in the dermis close beneath the basement membrane. The vast majority of all types of dendritic cells in normal human skin was of immature phenotype, i.e. did not express DC-LAMP/CD208. It is concluded that normal appearing human skin harbors different subsets of dendritic cells including few scattered BDCA-2-expressing cells, presumably plasmacytoid dendritic cells, expressing variable sets of C-type lectin receptors. This may critically contribute to the capacity of the skin immune system to flexibly respond to the world of microbial pathogens.

Dendritic cells (DCs) critically regulate immune responses and the "immune-surveillance" of tumours. This study retrospectively analysed the distribution and maturation status of DC-subsets in T-cell lymphoma of the skin. Mycosis fungoides and Sézary syndrome (n = 25) were investigated immunohistochemically for DC subsets, based on C-type lectin receptor expression: Langerhans' cells (langerin/CD207+, DEC-205/CD205+), dermal DCs (DC-SIGN/CD209+, CD205+) and plasmacytoid DC (BDCA-2/CD303+). Maturation status was assessed by double-labelling for CD83 and CD208/DC-LAMP. DCs were interspersed between the neoplastic infiltrate, and a marked increase in numbers of all three subsets was noted, DC-SIGN+ dermal DCs constituting the majority. Substantial numbers of plasmacytoid DCs were consistently observed. Most DCs in epidermis and dermis were phenotypically immature. Amongst the relatively few mature DCs in the dermis, langerin+ cells predominated. There was a positive correlation between the histological intensity of the tumour infiltrate and DC numbers. It is possible that mature DCs reflect ongoing anti-tumour immune responses, and immature DCs the induction of tumour tolerance.

SIR, We report a rare case of inhaler-induced burn in a 13-year-old boy caused by applying the nozzle of the inhaler to his hand and discharging the inhaler.A 13-year-old boy presented with a 4-day history of blisters around the edge of an erythematous patch on the dorsum of his left hand, which had been present for a year. His sister suffered from asthma. On examination, there was a welldemarcated erythematous patch on the dorsum of his left hand with crusts from ruptured blisters around the edge of the patch (Fig. 1). On further questioning, he admitted having developed this red patch 1 year previously after he had applied the nozzle of his sister's salbutamol inhaler onto his hand and discharged it a few times playfully. The repetition of this practice had resulted in the inhaler-induced burns we see in this picture.Inhaler-induced burn is very rare, and to our knowledge there are only three cases reported in the literature. 1-3 All three patients were asthmatic. Chemical burn from the pharmaceutical ⁄preservative ⁄propellant aerosol, cold injury to the skin or mechanical abrasive effect of the aerosol blasts were the suggested mechanisms of injury. Burge et al. suggested that the physical signs of inhaler-induced burn are similar to those seen after a standardized cryotherapy freeze injury to the skin. 4 Children who gain access to inhalers may find them to be interesting toys. They could then sustain chemical burns due to inappropriate discharge onto the skin. We need to be aware of this effect of commonly used inhalers and warn parents, teachers and children in order to avoid these injuries.