Evaluation of immunotoxicity induced by propoxure in C57Bl/6 mice

Insecticides are important candidates for immunotoxicology tests in order to assess the 'No Observable Adverse Effect Level' (NOAEL). Propoxure (PPX), as a carbamate household insecticide, has been used for several decades around the world in agriculture. However, there has been no clear investigation on its immunotoxic potentials. In this study, as Tier I of immunotoxicological screening tests, we examined the effects of subacute exposure to intraperitoneally (i.p.) administered PPX, at doses of 10, 2, and 0.2 mg/kg, on C57Bl/6 female mice. After 28 days administration of PPX, the treated animals were sacrificed and peripheral blood samples were collected. Then spleen (SP), thymus (TM), and bone marrow were collected and weighed. Functional tests including SRBC-hemagglutination (HA), plaque-forming colony assay (PFC), and delayed type hypersensitivity (DTH) response to SRBCs were performed. Furthermore, spleen T-cell phenotype (CD4/CD8) was also determined. Results showed that high doses of PPX could not only produce histopathological changes in TM and SP but also suppress humoral response to antigen (SRBCs). PPX at medium doses (2 mg/kg) did not show histopathological changes in TM or SP but increased the humoral response to SRBCs, as identified by HA and PFC tests. PPX at low doses (0.2 mg/kg) did not produce any significant changes in humoral (PFC and HA) or cellular responses (DTH) of the immune system. It seems that PPX has no adverse effects on mice immune system at low doses of 0.2 mg/kg/day, which is 10 times the PPX allowed daily intake (ADI) limit.