Is chronic exposure to low-dose organochlorine pesticides a new risk factor of T-cell immunosenescence?

Background: T-cell immunosenescence, a hallmark of an aging immune system, is potentially linked to the risk of developing cancer and other aging-related diseases. Chronic infection by cytomegalovirus (CMV) has been widely studied as a risk factor for T-cell immunosenescence, but the role of persistent chemicals has never been examined. As a typical example of persistent chemicals, we evaluated whether organochlorine pesticides (OCPs) are related to T-cell immunosenescence in the general population. Methods: Serum concentrations of β-hexachlorocyclohexane, p,p′-DDT, p,p′-DDE, and trans-nonachlor were measured in 95 Korean adults ages 30 to 64 years. T-cell immunosenescence was assessed by the frequencies of CD8⁺CD57⁺, CD8⁺CD28^-, CD4⁺CD57⁺, and CD4⁺CD28^- T lymphocytes in 20 mL of fresh peripheral blood. Results: The senescence of CD8⁺ T lymphocytes was the most consistently associated with OCPs. For quartiles of measurements of OCPs, adjusted mean percentages of CD8⁺CD57⁺ and CD8⁺CD28^- T lymphocytes in the CD8⁺ T lymphocyte population were 23.9, 27.6, 31.0, and 38.7 (P_trend < 0.01) and 25.6, 27.3, 28.0, and 35.5 (P_trend = 0.02), respectively. When we compared the strength of the associations among OCPs, CMV IgG titer, and age, OCPs showed the strongest association with markers of immunosenescence. Importantly, the association between OCPs and immunosenescence markers was more prominent among participants without known risk factors, such as a young age or low CMV immunoglobulin G titer. Conclusions: Chronic exposure to low-dose OCPs may be a new risk factor for T-cell immunosenescence. Impact: T-cell immunosenescence may be one possible mechanismlinking low-doseOCPs andmany chronic diseases.