The Hidden Threat: Environmental Level of Organotin Compromises Immunity

Abstract Tributyltin (TBT) is an environmental contaminant whose immunotoxic potential has been increasingly recognized, despite an established safe exposure limit of 250 ng/kg/day. This study evaluated the immunological effects of acute TBT exposure at 100 ng/kg/day, a dose 2.5 times below the WHO threshold, on BALB/c mice. Male mice received TBT or vehicle (0.4% ethanol) by gavage for 14 days. Body and organ weights were monitored, and spleen and bone marrow cells were analyzed by flow cytometry (CD4, CD8, FOXP3, B220, IgM, CD11b). Total serum IgG, IgM and IgE were measured by ELISA, and in vitro cytokine secretion by anti-CD3-stimulated splenic T cells was assessed. TBT suppressed myeloid cells, B cells, and several T cell subsets peripherally, and impacted central B cell production. Serum immunoglobulin levels remained unchanged. However, IL-6, IL-10, and IL-2 secretion by stimulated T lymphocytes was significantly decreased. These findings indicate that TBT at a dose below the WHO safe threshold induces significant immunosuppression in BALB/c mice, supporting the need to reassess the current acceptable daily intake.