Allergenicity testing of supermethrin, phenoxyacetic acid and DNCB using in vivo and in vitro modifications of the local lymph node assays, maximization and epicutaneous testing.

The purpose of this study was to compare two methods of testing for allergenicity: in vivo and in vitro modifications of local lymph node assays (LLNA) in mice and the maximization and epicutaneous skin tests in guinea pigs as per the Organization for Economic Cooperation and Development (1981). Two pesticides-the synthetic pyrethroid insecticide supermethrin (SM) and the herbicide phenoxyacetic acid (PAA)-were evaluated using this testing battery. 1-Chloro-2,4-dinitrobenzene (DNCB) was selected as a reference allergen for the local lymph node assay. In vitro modification of LLNA proliferative response per standard cell count in lymphocyte cultures derived from treated Balb/c mice did not differ from control mice. Results of the in vivo modification showed that treatment with 50% PAA and 50% SM resulted in a lower proliferation response of lymphocytes in lymph nodes compared with control animals. The vigour of the proliferative response varied more in in vivo modification of LLNA. Stimulation indices were <3, so PAA and SM did not indicate classification as allergens. Lymphocyte proliferation in 1% DNCB-activated lymph nodes was approximately fivefold higher than in those derived from control mice. Proliferation response in vitro calculated as stimulation index was higher in DNCB-treated mice than those observed in vivo, but differences were not dramatic. Auricular lymph node weight and cellularity in mice treated with PAA and SM were similar to controls. The DNCB stimulation index for lymph node cellularity was 5.5. Lymph node weight was three times higher in comparison with controls. In the maximization test in guinea pigs SM and PAA acid resulted in 40% and 50% of animals demonstrating sensitization, respectively. Epicutaneous administration resulted in weaker reaction. Both SM and PAA are mildly strong sensitizers by this battery.