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There are currently no skin sensitization assays based on T cell activation. We built a novel in vitro model to assess T cell activation and test its performance to discriminate skin sensitizers from non-sensitizers using 52 reference chemicals. Jurkat Clone E6-1 human T lymphocytes were exposed to a series of concentrations of test substances for 24 hours and CD69 expression was measured as a marker of early T cell activation with flow cytometry. Most tested sensitizers induced increased relative fluorescence intensity (RFI) of CD69 on the T cells, which was linearly correlated with the concentrations tested, indicating a statistically significant causal link between sensitizer concentration and increase of CD69 expression. CD69 RFI ≥ 1.5 was determined as the positive criterion for skin sensitizer classification. The sensitivity (79.4%), specificity (88.9%) and accuracy (82.7%) of the model for the 52 tested reference chemicals showed a good predictivity for skin sensitizers. The results were reproduced in at least two repeats; and the concurrent positive control, 2 µg/mL 2, 4-dinitrochlorobenzene, was found positive in all 25 independent runs conducted, indicating in-house reproducibility. The EC1.5 value (i.e., the concentration at which a test chemical induces a CD69 RFI of 1.5) may be used to assess skin sensitization potency of a chemical. This work may contribute to the development of an in vitro assay for skin sensitization based on the activation of T cells.
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