Pyrethroids and piperonyl-butoxide affect human T-lymphocytes in vitro

Abstract Synthetic pyrethroids are increasingly used as insecticides and are claimed to have a relatively low human toxicity. The aim of this study was to examine the in vitro effects of the synthetic pyrethroid S -bioallethrin alone and in combination with the common synergist piperonyl-butoxide (PBO) on human blood lymphocytes and basophils in atopic individuals and non-atopic control subjects. S -bioallethrin and PBO also caused inhibition of lymphocyte proliferation (MTT-test) after a 72-h culture period in a concentration dependent manner. In contrast to the MTT-measurements the combined agents are more effective in inhibiting interleukin-4 (IL-4)- and interferon-γ (IFN-γ)-production. The regulatory IL-4/IFN-γ balance showed a significant difference between atopic and non-atopic subjects after a culture period of 24–48 h in the presence of micromolar S -bioallethrin ( P S -bioallethrin, PBO and the combined agents induced histamine release from human basophils. Although this effect was little compared to histamine liberators like FMLP and anti-IgE, the response to S -bioallethrin and PBO was significantly different in atopic donors compared with non-atopics ( P S -bioallethrin and permethrin, whereas no reaction could be measured in the control group (age-matched). These findings demonstrate the immuno- and allergo-toxicological properties of the synthetic pyrethroid S -bioallethrin combined with the synergistic PBO using this in vitro approach with human lymphocytes and basophils.