Minimal uranium immunotoxicity following a 60-day drinking water exposure to uranyl acetate in male and female C57BL/6J mice

Highlights: • Drinking water uranium exposure (uranyl acetate) produced minimal immunotoxicity in male or female C57BL/6J mice. • Innate immune cell subsets were slightly reduced in male, but not female mice. • Mature splenic lymphocyte function was not significantly altered in male or female mice. -- Abstract: Historical uranium (U) mining in the Southwestern United States resulted in significant environmental contamination throughout this region and presents a significant risk of chronic metal exposure and toxicity for communities living in close proximity to mine waste sites. Uranium exposure is associated with numerous deleterious health effects including immune dysfunction; however, its effects on the immune system have yet to be fully characterized. We recently published that drinking water exposure to U, in the form of uranyl acetate (UA), results in low overall tissue retention of U ( < 0.01%), with very little accumulation in immune organs (blood, bone marrow, spleen, and thymus) of male and female mice. In the present study we characterized the immunotoxicity of U, in the form of UA, following a 60-day drinking water exposure to 5 and 50 ppm in male and female C57BL/6J mice. The following immunotoxicity endpoints were evaluated: hematology, immune tissue weights and total cell recoveries, immunophenotying of the spleen and thymus, and immune cell function (lymphocyte mitogenesis and T-dependent antibody response). Uranium exposure had subtle impacts on the immune endpoints evaluated, likely due to low U accumulation at these sites. The only significant alterations were a slight decrease in the percentages of splenic natural killer T-cells and macrophages in exposed male mice. Despite minimal immunological effects, this study highlights the importance of investigating toxicological endpoints in both sexes and developing accurate animal models that model epidemiological exposures in the future.