Abstract
Trichloroethylene (TCE) is a volatile chlorinated organic compound that is commonly used as a solvent for lipophilic compounds. Although recognized as an animal carcinogen, TCE’s carcinogenic potential in humans is still uncertain. We have carried out a cross-sectional study of 80 workers exposed to TCE and 96 unexposed controls matched on age and sex in Guangdong, China to study TCE’s early biologic effects. We previously reported that the total lymphocyte count and each of the major lymphocyte subsets (i.e., CD4+ T cells, CD8+ T cells, natural killer cells, and B cells) were decreased in TCE-exposed workers compared to controls, suggesting a selective effect on lymphoid progenitors, and/or lymphocyte survival. To explore which T lymphocyte subsets are affected in the same study population, we investigated the effect of TCE exposure on the numbers of CD4+ naïve and memory T cells, CD8+ naïve and memory T cells, and regulatory T cells by FACS analysis. Linear regression of each subset was used to test for differences between exposed workers and controls adjusting for potential confounders. We observed that CD4+ and CD8+ naïve T cell counts were about 8% (p = 0.056) and 17% (p = 0.0002) lower, respectively, among exposed workers. CD4+ effector memory T cell counts were decreased by about 20% among TCE-exposed workers compared to controls (p = 0.001). The selective targeting of TCE on CD8+ naive and possibly CD4+ naive T cells, and CD4+ effector memory T cells, provide further insights into the immunosuppression-related response of human immune cells upon TCE exposure.
Highlights
Trichloroethylene (TCE) is a volatile chlorinated organic compound that is used as a degreaser for metal parts and a generalpurpose solvent for lipophilic compounds
To explore which T lymphocyte subsets are affected in the same study population, we investigated the effect of TCE exposure on the numbers of CD4+ naïve and memory T cells, CD8+ naïve and memory T cells, and regulatory T cells by FACS analysis
While no differences were observed between the regulatory T cells among controls and exposed workers, we did observe that occupational exposure to TCE decreased CD4+ effector memory T cell, CD4+ naïve T cell, and CD8+ naïve T cell counts
Summary
Trichloroethylene (TCE) is a volatile chlorinated organic compound that is used as a degreaser for metal parts and a generalpurpose solvent for lipophilic compounds. While TCE has been deemed an animal carcinogen, its carcinogenicity potential in humans has not been fully characterized (IARC, 1995). Epidemiological studies have found associations between TCE exposure and cancers of the kidney and liver, and non-Hodgkin lymphoma (NHL; Raaschou-Nielsen et al, 2003; Scott and Chiu, 2006; Alexander et al, 2007; Kelsh et al, 2010; Purdue et al, 2010). To better understand the human health effects associated with TCE, we carried out a cross-sectional study to evaluate the biologic plausibility of NHL associated with occupational exposure to TCE in Guangdong, China (Lan et al, 2010). The primary goal of this study was to follow up experimental studies indicating TCE’s potential to alter key lymphocyte subset levels, such as CD4+
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