Abstract: OBJECTIVE: To establish and evaluate a modified local lymph node assay incorporated with bromodeoxyuridine and enzyme-linked immunosorbent assay. METHODS: Female BALB/c mice were organized into several groups of 4 mice per group:solvent control (AOO, ACE, DMSO or distilled water), positive control (25% hexyl cinnamaldehyde) and test substance (22 chemicals and 5 cosmetics were selected to form 1-3 different concentrations) groups. The dorsal sides of both ears of mice were treated with 25 μL/ear of test solutions at 9:00 am on 3 consecutive days with no treatment on day 4. BrdU solution was injected interperitoneally on day 5 with 0.5 mL per mouse. On day 6, ear punches were collected and weighted. The bilateral draining auricular lymph nodes were excised and made into single cell suspensions from which lymphocyte proliferations were measured using the BrdU ELISA kit. RESULTS: Ear punch weights from mice treated with 50% hexyl cinnamic aldehyde,5% cobalt dichloride,10%,25%,50% lactic acid and No.2 hair dye were increased significantly (P < 0.05 or P < 0.01),which might be considered as irritants. The others were negative. For LLNA, 15 chemicals (2,4-dinitrochloro-benzene, eugenol, isoeugenol, 3-aminophenol, transcinnamic aldehyde, hexyl cinnamic aldehyde, geraniol, hydroquinone, hexyl salicylate, formaldehyde, glutaraldehyde, nickel sulfate, cobalt dichloride, potassium dichromate, lactic acid) and No.2 hair dye were positive (SI>1.6),and the others were negative. The method was evaluated with positive prediction rate 93.3%, negative prediction rate 100%,false positive rate 14.3%,false negative rate 0,sensitivity 100%,specificity 85.7% and accuracy 95.2%. CONCLUSION: The LLNA:BrdU-ELISA assay using BALB/c mice appears to be useful for predicting sensitization and irritancy potential,and for safety evaluation of cometics.

Key words: local lymph node assay, sensitization, irritancy, cosmetics, BALB/c mouse