What is a Skin Sensitizer?
In Vitro Assays
Upon exposure to skin sensitizers, the KeratinoSens™ Test measures activation of Keap1-Nrf2-antioxidant/electrophile response element (ARE). These tests use an immortalized, adherent, human keratinocyte cell line (HaCaT) that was transfected with a plasmid to monitor luciferase gene induction.
To determine the skin sensitization potential of a test article due to cell activation by the measurement of changes in the expression of dendritic cell surface markers (CD86, CD54) via flow cytometry. The THP-1 human monocytic cell line serves as the test system. The h-CLAT is recommended by EURL ECVAM as part of an Integrated Approach to Testing and Assessment (IATA) to support the discrimination between sensitizers (i.e., UN GHS Category 1) and non-sensitizers for the purpose of hazard classification and labeling, per OECD Guideline 442E “In Vitro Skin Sensitization: Human Cell Line Activation Test (h-CLAT)”.
Developed and designed by MB Research Labs, the IVSA is an in vitro test that quantifies interleukin‐18 (IL‐18) release from keratinocytes following test article (TA) administration to reconstructed human epithelial (RhE) tissue. TIL‐18 is quantified via a commercial ELISA kit. IL‐18 release from TA‐treated tissues is compared that of vehicle‐treated controls. Solids, extracts, mixtures, insoluble chemicals and soluble chemicals are eligible for evaluation via the IVSA. Results are used to support the discrimination between sensitizers and non-sensitizers, and can be used for potency ranking.
The DPRA is an in chemico method that quantifies cysteine‐ or lysine‐containing peptide depletion following 24 hours incubation with the test article (TA). Relative peptide concentration is measured by HPLC with gradient elution and UV detection at 220 nm. Cysteine and lysine peptide percent depletion values are then calculated and used in a prediction model, which allows assigning the TA to one of four reactivity classes used to support the discrimination between sensitizers and sonosensitizers.
Contact dermal sensitization is an immunological process where the host, through repeated skin exposure, acquires a specific allergic sensitivity to a substance. In the Buehler model, contact dermal sensitivity is manifested as increased erythema.