Session A8: Skin Sensitization

Chairs: Ian Kimber (UK) and Frank Gerberick (USA)

A8: Understanding the Chemical Basis of Contact Allergy in the Development of Alternative Methods
Frank Gerberick. The Procter & Gamble Company, P.O. Box 538707, Cincinnati, OH 45253-8707, USA. gerberick.gh@pg.com.

A8: A Genomics Approach for the Development of an In Vitro Method for Skin Sensitization
C.A. Ryan¹, B.C. Hulette¹, R.J. Dearman², I. Kimber², and G.F. Gerberick¹. ¹The Procter & Gamble Company, P.O. Box 538707, Cincinnati, OH 45253-8707, USA; ²Syngenta CTL, Macclesfield, UK. ryan.ca@pg.com.

For the development of an in vitro method for predictive skin sensitization testing, a genomics approach is being used to elucidate pathways that are involved in the immune recognition of chemical allergens by dendritic cells (DC) and T-cells, key cells involved in the induction and elicitation of allergic contact dermatitis. The aims are to identify and characterize genes that provide sensitive, selective, and robust markers of sensitization and that allow discrimination between contact allergens and skin irritants. To gain an understanding of the changes in gene expression induced by antigen-specific T-cell/DC interactions in humans, we examined T cell activation via the T cell receptor, using anti-CD3, in an in vitro co-culture system comprised of peripheral blood-derived DC and responding T cells was used. Changes in gene expression of >2-fold were observed in 108 genes, ranging +42-fold to –10-fold. This information will be used as a benchmark in examining secondary and primary responses in T cells co-cultured with hapten-treated DC.

A8: In Vitro Prediction of Contact Sensitivity: Success Will Arise from Combination of Different Technologies
F. Rousset, D. Verda, J.-L. Garrigue, V. Facy, M. Régnier, M. Mariani, and J. LeClaire. L'Or&eaucte;al Life Sciences- Advanced Research- Aulnay-sous-Bois, France.

Contact sensitivity is a T-cell mediated immune response to low molecular weight chemicals that penetrate through the skin. Identification of the major steps and actors involved in the elaboration of this multi-parametric and complex reaction opens new insight into alternatives to animal testing. Focus on the early common events leading to contact sensitivity has allowed emergence of in vitro tests that are able to discriminate sensitizers from irritant reference ingredients. This approach is based on the utilization of in vitro-generated human dendritic cells (DC), surrogate DC-cell lines, and 3D-reconstructed epidermis that integrate Langerhans cells. Co-cultures with keratinocytes, or autologous T lymphocytes (for « latter » events), are also integrated in this research field. A huge battery of complementary technologies, from cell surface analysis, endocytosis, second messengers analysis, metabolism, RTPCR, to toxicogenomics are now being investigated. A cellular model, based on the modulation of cell surface markers (CD86, MHC-class I) on the pro-monocytic human cell line U937, is already predictive of the intrinsic sensitizing potential of chemicals (more than 50 references tested). Finally, a strategy alternative to animal testing and leading to the hazard and to the risk assessment will be proposed.