Development of non-radio isotopic endpoint of murine local lymph node assay based on 5-bromo-2 '-deoxyuridine (BrdU) incorporation

Allergic contact dermatitis is a serious health problem. Over the last deca de, the murine local lymph node assay (LLNA) has been developed to detect c hemical allergens, and international validation studies have been conducted . We have tried to establish an alternative non-radioisotopic endpoint for the LLNA by using 5-bromo-2'-deoxyuridine (BrdU) incorporation in place of radioisotopes, such as [H-3]thymidine, employed in the standard method. Brd U was given as a single administration at 5 mg/animal 2 days following thre e consecutive daily. applications of a test chemical. BrdU incorporation in to draining lymph node cells was measured using an enzyme immunosorbent ass ay technique. In this study, p -benzoquinone(PBQ), trimellitic anhydride (T MA), citral(CT) and dextran (DEX) were used as pilot chemicals. PBQ, TMA an d CT, which are classified as moderate to strong sensitizers in the guinea pig maximization test and were positive in the original LLNA, were also fou nd to elicit positive responses in the alternative LLNA using BrdU incorpor ation. In contrast, DEX tested negative in the modified assay consistent wi th previous guinea pig and LLNA data. Consequently, the modified LLNA endpo int using BrdU incorporation may represent a useful alternative to the stan dard assay in situations, where there is a need to avoid the use of radiois otopes. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.