Use of the LLNA:BrdU-ELISA for Skin Sensitization Hazard Assessment.

Allergic contact dermatitis (ACD) continues to be an occupational and environmental health issue. Consequently, there is a need to employ predictive tests to reduce the incidence of skin sensitization leading to clinical manifestations of ACD. For more than a decade, the murine local lymph node assay (LLNA) has been the method of choice for the identification of skin sensitizers. While the original LLNA protocol has been extensively evaluated and subjected to exhaustive validation, the use of radioisotope (i.e., tritiated thymidine; 3HTdR) has discouraged utilization of this powerful assay in some countries. To promote further utilization of this method, the original LLNA protocol was refined to use 5-bromo-2'-deoxyuridine, a nonradioactive analog of 3HTdR. The LLNA:BrdU-ELISA has been reviewed, validated, and approved for use internationally, and its performance is regarded as equivalent to the traditional LLNA. Here, we provide guidance on how to perform and interpret data from this assay.