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 allerge nicity: in vivo and in vitro modifications of local lymph node assays (LLNA ) in mice and the maximization and epicutaneous skin tests in guinea pigs a s 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 batter y. 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 coun t in lymphocyte cultures derived from treated Balb/c mice did not differ fr om control mice. Results of the in vivo modification showed that treatment with 50% PAA and 50% SM resulted in a lower proliferation response of lymph ocytes in lymph nodes compared with control animals. The vigour of the prol iferative response varied more in in vivo modification of LLNA. Stimulation indices were <3, so PAA and SM did not indicate classification as allergen s. Lymphocyte proliferation in 1% DNCB-activated lymph nodes was approximately fivefold higher than in those derived from control mice. Proliferation res ponse in vitro calculated as stimulation index was higher in DNCB-treated m ice than those observed in vivo, but differences were not dramatic. Auricul ar lymph node weight and cellularity in mice treated with PAA and SM were s imilar to controls. The DNCB stimulation index for lymph node cellularity was 5.5. Lymph node w eight 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 adm inistration resulted in weaker reaction. Both SM and PAA are mildly strong sensitizers by this battery. Copyright ((C) 2001 John Wiley & Sons, Ltd.