Assessment of the human Cell Line Activation Test (h-CLAT) for Skin Sensitization; Results of the First Japanese Inter-laboratory Study

The human Cell Line Activation Test (h-CLAT) is an in vitro skin sensitization test based on the enhancement by sensitizers of CD86 and/or CD54 expression on THP-1 cells. The aim of this study is to confirm the transferability and reproducibility of the h-CLAT protocol. Seven Japanese laboratories participated in this h-CLAT ring study. First, two well-known sensitizers (dinitrochlorobenzene (DNCB) and nickel sulfate (Ni)) and one non-sensitizer (sodium lauryl sulfate (SLS)) were evaluated at each laboratory with the same protocol at the same application dose. All laboratories correctly evaluated the skin sensitization potential of these three chemicals. Next, four sensitizers and one non-sensitizer were tested as a second trial. There were two false-negatives (ethylene diamine and eugenol) in some laboratories. Finally, chemicals tested in the second trial were re-evaluated with doses individually determined by each laboratory as a third trial. The results were almost the same as the results obtained when all the laboratories tested the same application doses. These results suggest that for more precise evaluation of difficult samples (e. g., unstable or water-insoluble chemicals), modifications of the protocol and prediction model are needed. However, the protocol was easily transferred to all laboratories and there were only a few false-negatives among 56 tests (8 chemicals at 7 laboratories).