The h-CLAT test method is an in vitro toxicology assay that evaluates cell surface marker expression - CD86 and CD54 on THP-1 cells, a human monocytic leukemia cell line following a 24 hrs exposure to a test substance. CD86 and CD54 are surface molecules that are typical markers of Dendritric Cell (DC) activation and play an important role in T cell priming. Cell surface marker expression is measured by flow cytometry following fluorescent staining with fluorochrome-tagged antibodies. Assessment of surface markers expression at sub-cytotoxic concentrations is also assessed concurrently. The relative fluorescence intensity of the surface markers is calculated by comparing results to vehicle control are calculated and used in the h-CLAT prediction model, allowing for discrimination between sensitizers and non-sensitizers.
OECD Test Guideline 442E has been approved for use as of 9 October 2017. Previously, the h-CLAT has been evaluated in a European Union Reference Laboratory for Alternatives to Animal Testing (EURL-ECVAM) and was considered scientifically valid to be used as part of an intergrated approach to testing and assessment (IATA) for discrimination between sensitizers and non-sensitizers for hazard classification and labelling.