ABSTRACT
<p><b>BACKGROUND</b>The sensitization and elicitation phases are involved in the immunopathogenesis of contact hypersensitivity (CHS). Langerhans cells (LCs) are believed to play pivotal roles in the sensitization stage of CHS. Local hyperthermia on skin induces the migration as well as maturation of epidermal LCs. Although fever-range whole body hyperthermia and local hyperthermia at 43°C prior to sensitization were reported to suppress CHS, the effects of different temperatures and the timing sequence of local hyperthermia on CHS have not been tackled.</p><p><b>METHODS</b>Local hyperthermia was applied to murine dorsal skin 3 days prior to, concurrent with, or 2 days post sensitization with fluorescein isothiocyanate (FITC) in BALB/c mice. Local hyperthermia temperatures at 37°C, 39°C, 41°C and 43°C were applied to mouse dorsal skin and the severity of CHS was calculated by measuring the swelling response of the challenged ears.</p><p><b>RESULTS</b>Local hyperthermia at 39°C, 41°C and 43°C prior to sensitization reduced the severity of CHS, as compared with that at 37°C. The suppression of CHS was temperature dependent in that higher temperature had a stronger effect. On the contrary, the hyperthermia treatments, either concurrent with or post-sensitization, resulted in an enhanced temperature-dependent ear swelling response.</p><p><b>CONCLUSIONS</b>The severity of murine CHS could be influenced by local hyperthermia at the sensitization stage in a temperature dependent manner. The temporal effect of local hyperthermia suggested a novel factor in interpreting the severity of allergic contact dermatitis.</p>