Effect of chlorpyrifos on the profile of subpopulations immunocompetent cells B, T and NK in in vivo model.

Background: Current studies have indicated many environmental factors, such as pesticides, that cause immune system disorders through inducing changes in humoral and cellular responses thereby increasing the risk of contracting infectious diseases and cancer. The literature suggests that low exposures to certain organophosphorus pesticides stimulate the immune system, whilst high exposures result in decreased function. Precise mechanisms for the fall in immunocompetence are often unclear, however it can be predicted that the intimate interaction between the nervous and immune systems can potentially lead to toxicity.

Objectives: To determine the effects of organophosphorus pesticide, chlorpyrifos that is often used in Poland, on selected immunological responses, such as immune-competent cell proportions formed experimentally in-vivo by cells of Wistar rats during subchronic exposures after 45 and 90 days.

Materials And Methods: The test was carried out on ten male and ten female Wistar rats in each of three test groups, who received 3 chlorpyrifos doses for 90 days intragastrically, according to OECD guidelines (No. 401). Two control groups were given olive oil. After completion, the animals were deeply anaesthetised by a mixture of ketamine (Vetaketam) and xylazine (Vetaxym). Immuno-competent cells were profiled by a commercial monoclonal antibody method. In order to measure the dynamics of any changes, the aforementioned immunological responses were investigated after 45 days using the same procedures for obtaining the relevant biological test material.

Results: Test animals exposed to chlorpyrifos had altered number of white bood cells which were either increased or decreased relative to controls after 45 and 90 days for all exposure levels used.

Conclusions: The study demonstrated changes in white-blood cell (lymphocyte) response profiles, reflecting an immunomodulation although such changes were equivocal, where both suppression and stimulation were observed.

Key Words: immunomodulation, immune system, lymphocyte, organophosphorus pesticides, chlorpyrifos.