Selective Induction of Interleukin-12 in Reconstructed Human Epidermis by Chemical Allergens

Emanuela Corsini, Elena Limiroli, Marina Marinovich, Catherine
Cohen, Roland Roguet and Corrado L. Galli

Keratinocytes play an important role in skin inflammatory and immunological reactions through the release of cytokines and response to them. These cells have been shown to direct T-cell priming by producing cytokines such as interleukin (IL)-10 and IL-12. The purpose of this work was to explore the potential use of IL-12 production to discriminate between skin irritants and contact allergens in vitro. Initially, a reconstituted human epidermis was treated with a known human skin irritant, sodium lauryl sulphate (SLS), and a known human contact allergen, 1-chloro-2,4-dinitrobenzene (DNCB). The expression of IL-12p40 was assessed at specific time intervals by the semi-quantitative reverse transcriptase-polymerase chain reaction (rt-PCR). The data obtained indicated that only DNCB induced an up-regulation of IL-12p40. This up-regulation occurred after exposure to DNCB for 3 hours. Importantly, the application of SLS or vehicles did not induce IL-12 mRNA up-regulation. An increase in total IL-12 protein content was detected in supernatants of allergen-stimulated, but not vehicle-stimulated, reconstituted epidermis. To confirm these results, the effects of benzalkonium chloride, oxazolone and eugenol were assessed. At concentrations that resulted in equivalent IL-1α release, only contact allergens increased IL-12 expression, which confirmed the previous results. These data suggest that IL-12, which is crucial for T-helper type 1 cell responses, could be a useful marker for discriminating between contact allergens and irritants.
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Immunotoxicology: Opportunities for Non-animal Test Development

Emanuela Corsini and Erwin L. Roggen

At present, several animal-based assays are used to assess immunotoxic effects such as immunosuppression and sensitisation. The use of whole animals, however, presents several secondary issues, including expense, ethical concerns and relevance to human risk assessment. There is a growing belief that non-animal approaches can eliminate these issues without impairing human safety, provided that biological markers are available to identify the immunotoxic potentials of new chemicals to which humans may be exposed. Driven by the 7th Amendment to the EU Cosmetics Directive, the new EU policy on chemicals (the REACH system), proposals to update the European legislation on the protection of animals used in research, and emerging visions and strategies for predicting toxicity, such in vitro methods are likely to play a major role in the near future. The realisation that the immune system can be the target of many chemicals, resulting in a range of adverse effects on the host’s health, has raised serious concerns from the public and within the regulatory agencies. Hypersensitivity and immunosuppression are considered the primary focus for developing in vitro methods in immunotoxicology. However, in vitro assays to detect immunostimulation and autoimmunity are also needed. This review of the state-of-the-art in the field of in vitro immunotoxicity, reveals a lack of cell-based immunotoxicity assays for predicting the toxicity of xenobiotics toward the immune system in a simple, fast, economical and reliable way.
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