Serotonin in human allergic contact dermatitis. An immunohistochemical andhigh-performance liquid chromatographic study

Allergic contact dermatitis (ACD) is a common clinical condition leading to considerable morbidity, We have recently demonstrated that ketanserin, a s erotonin antagonist, significantly inhibits nickel sulphate-induced ACD. Fu rthermore, serotonin-immunoreactive (IR) cells have previously been demonst rated in normal human cutaneous melanocytes, To further elucidate the role of serotonin in cutaneous contact hypersensitivity, we compared ACD involve d skin and uninvolved skin from nickel-allergic patients, and normal skin f rom healthy volunteers, for the presence of serotonin-like immunoreactive c ells using immunohistochemistry, In addition, serotonin concentrations in A CD involved and uninvolved skin were compared by high-performance liquid ch romatography (HPLC). In the skin of normal healthy volunteers, the serotoni n-IR cells were situated in the basal layer of the epidermis, In uninvolved skin the cells were also situated in the basal layer, but they were more n umerous and the immunofluorescence intensity was greater. In involved skin, the IR cells were fewer and they were found higher up in the epidermis, Al so, the configuration of these cells was different: they showed enlarged an d elongated dendrites as well as dendritic spines. The serotonin antiserum- labelled cells in ACD involved skin were also NKI-beteb positive (the latte r is known as a reliable marker of melanocytes), The concentration of serot onin in involved skin was significantly higher than that in uninvolved skin in ACD patients (P < 0.05), Taken together, our previous and present resul ts indicate that serotonin plays an important role in ACD, The basal epider mal serotonin-IR cells are more dendritic in ACD, and are found more superf icial in the epidermis, where they might release their content of serotonin , thereby influencing the inflammatory process.