Application of sensitive mouse lymph node assay for detection of contact sensitization capacity of dyes

A sensitive mouse lymph node assay (SLNA) is a test method for the detection of contact allergens. The sensitization potential of test chemicals is determined by assessing total lymph node activation response induced by application of the chemical. In this study, we examined whether the SLNA would have a sufficient competence for determination of sensitization capacity of coloured chemicals routinely. Prior to this study, we investigated application of an Alamar Blue dye (non-radioisotope reagent) as an alternative to [3H]thymidine for measurement of cell proliferation. However, the Alamar Blue assay is useful for determining cell number but is not applicable to detect lymph node cell proliferation activity for 24-h culture in the SLNA. The SLNA was applied to evaluate the sensitization capacity of 20 dyes. Most of the sensitizing dyes were correctly determined as a sensitizer. Some chemicals that were known as strong sensitizers showed strong lymph node responses. Comparing the results of the SLNA with data from guinea-pig tests, the same predictions of sensitization capacity were made in nine out of ten cases. The SLNA also detected 13 of the 17 chemicals that were identified to be contact allergens by the human patch test. These data showed that the evaluation of the SLNA was not influenced by the colour property of the test chemicals and that the SLNA was a sufficiently sensitive robust screen test for the identification of contact allergens.