Test Guideline No. 442E focuses on in vitro skin sensitisation assays that specifically target the activation of dendritic cells as part of the adverse outcome pathway for skin sensitisation. This guideline is aimed at assisting in the differentiation between skin sensitizers and non-sensitizers according to the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS).
Main Components:
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Background and Principles: The document outlines the background and principles behind the test methods that address the activation of dendritic cells, providing an alternative to traditional animal-based methods like the Guinea Pig Maximisation Test (GPMT) and the Buehler Test (TG 406). It highlights the advantages of using in vitro methods, particularly in terms of animal welfare and objective measurement of the induction phase of skin sensitisation.
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Assessment Methods:
- Human Cell Line Activation Test (h-CLAT): Evaluates the response of human cells to test chemicals.
- U937 Cell Line Activation Test (U-SENS™): Uses a specific cell line to detect skin sensitisation.
- Interleukin-8 Reporter Gene Assay (IL-8 Luc assay): Measures changes in the expression of IL-8, indicating cell activation.
- Genomic Allergen Rapid Detection (GARD™) for skin sensitisation (GARD™skin): Identifies genomic signatures associated with the activation of monocytes and dendritic cells.
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Mechanisms and Indicators: Skin sensitizers are known to induce specific cellular responses, including changes in cell surface markers (CD54, CD86), cytokine production (IL-8), and alterations in gene expression. These indicators are crucial for assessing the potential of chemicals to cause skin sensitisation.
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Limitations and Interpreting Results: The document acknowledges that while these test methods can support the discrimination between skin sensitisers and non-sensitisers, they do not suffice as standalone methods for conclusively determining skin sensitisation potential. They are recommended for use in combination with other relevant information sources within integrated approaches to testing and assessment.
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Applicability: The test methods are technically applicable to mono-constituent substances, multi-constituent substances, and mixtures, although considerations should be made for the meaningfulness of the results, especially when dealing with complex mixtures or unstable chemicals.
Conclusion:
Test Guideline No. 442E provides a comprehensive framework for in vitro skin sensitisation assays focused on dendritic cell activation. It supports the development of alternative, more humane, and scientifically robust methods for assessing skin sensitisation potential, complementing traditional testing methods and enhancing the safety evaluation of chemicals.
