Two-tiered approach to determine the skin sensitising capacity and potency of chemicals

Method Description

The 2-TA tiered approach addresses the capacity and the potency of a potentially sensitizing chemical on acute exposure to the chemical.

Human-derived epidermal-like cells (NCTC2544) are used to distinguish skin sensitizers from respiratory sensitizers and non-sensitizers (including irritants). This is the so-called 1st Tier or also called 'NCTC-assay'. The 2nd Tier or also called 'EE-potency assay' is used to estimate the potency of the identified sensitizing chemical. Human reconstituted epidermal skin-equivalents are used in this step.

The NCTC-assay is based on the effects of skin sensitizing chemicals on the production of pro-inflammatory intracellular IL-18 by human-derived NCTC2544 keratinocytes. The EE-assay is based on the inverse correlation between potency of a sensitizer and the viability of a human reconstituted epidermal model as determined by the MTT test and IL- 1 alpha release into the culture medium.