Other surveys on such contingents2931reported comparable results. occupational radiation exposure on T helper populations. Nevertheless, the observed even slight trends in some lymphocytes populations and in cytokines profile give us the reason to assume a possibility of a progressive polarization of T helper 1 to T helper 2 immune response at dose range 100 to 200 mSv. The results of the present study indicate the need to perform a more detailed epidemiological survey including potential confounding and misclassifying factors and possible selection bias that could influence the results. Keywords:T-cell populations, immunoglobulins, interleukins, low-dose ionizing radiation, NPP staff == Introduction == The radiation impact on the immune system as an integral part of the body determines the alterations in the homeostasis and/or in its components. Long-term epidemiologic studies demonstrate that ionizing radiation may induce a dose-dependent impartment of the immune system with a deregulation of cytokine production and persistent inflammation, which is HLI-98C supposed to increase the risk of both malignancy and noncancerous diseases.15The radiation-induced oxidative stress prospects to higher expression of some markers of inflammation such as adhesion molecules and cytokines, which when interacting with cells surface receptors activate specific mechanisms and stimulate immune response. T helper 1 (Th1) lymphocytes generating pro-inflammatory cytokines are induced immediately after irradiations, while T helper 2 (Th2) lymphocytes suppliers of anti-inflammatory cytokines restore homeostasis. The balance between pro- and anti-inflammation tendencies could fluctuate long after a radiation impact and will persist until the elimination of the stress factor. The published results on the effect of ionizing radiation around the Th1/Th2 balance and its influence on human health are controversial. They suppose a pronounced inflammatory effect of a high-dose exposure6and an anti-inflammatory effect at low-dose irradiation (single doses 1.0 Gy).7,8 The epidemiological studies of atomic bombing survivors and Chernobyl emergency and clean-up workers found long-term imbalance in Th1/Th2 responses shifted toward an inflammatory profile.14,911It is suggested15,9that doses in the range of 10 to 100 mGy lead to the prevalence of T1 helper subpopulation, while doses above 200 mGy switch to prevalence of T2 helper immune response. Experimental studies reveal a decrease after low-dose HLI-98C exposure and an increase after high-dose exposure of expression in both Th1 and Th2 type cytokines.12 The assessment of low-dose radiation on changes in immunological parameters and state of subclinical inflammation requires a careful examination of the immune status of occupationally uncovered persons. Our previous data on lymphocyte populations profiles in Nuclear Power Rabbit Polyclonal to RAN Herb (NPP) workers13,14raised the issue with respect to the prevalence of Th1 immune response at low-dose exposures and dominating of Th2 with increasing cumulative doses above 100 to 200 mSv. Therefore, the current study aims to extend the investigation on NPP workers with special focus on cytokine profilesinterleukin 2 (IL-2), interferon (IFN), IL-4, and T HLI-98C helper subpopulationsin order to determine some imbalance in Th1 and Th2 immune response. == Material and Methods == One Hundred five employees working in NPP, Kozloduy, Bulgaria, were included in the study. The group of men occupationally exposed to external radiation was selected from your support personnel of models 5 and 6 of NPP Kozloduy. A control group of 32 male participants was selected at similar age and with comparable length of support who do not have any work related to ionizing radiation. The study was carried out thanks to HLI-98C a contract between the National Centre of Radiobiology and Radiation Protection of the Ministry of Health of Bulgaria and the NPP Kozloduy. An informed verbal consent was obtained from all participants. The study was performed within the framework of a bilateral contract between the National Centre of Radiobiology and Radiation Protection, part of the Ministry of Health and NPP Kozloduy. The data for individual monitoring exposure were submitted by NPP Kozloduy dosimetry support, approved by the.