Developmental immunotoxicity in male rats after juvenile exposure to di- n-octyltin dichloride (DOTC)

► The utility of immune assays needs to be evaluated for assessing developmental immunotoxicity. ► TDAR parameters are appropriate for inclusion in developmental toxicity studies. ► Immunological evaluation at PND 21 and PND 42 revealed the most pronounced effects. ► Multiple time points are necessary for a complete assessment of developmental immune effects. ► Findings demonstrate the relative sensitivity of the developing immune system for DOTC. To determine relevant endpoints for evaluating developmental immunotoxicity due to juvenile exposure and optimal age of the animals at assessment, a wide range of immunological parameters were assessed in a juvenile toxicity study. Rats were exposed to di- n-octyltin dichloride (DOTC) by gavage from postnatal day (PND) 10 through PND 21 and via the diet after weaning using a benchmark dose (BMD) approach. Immune assessments were performed in male rats on PNDs 21, 42, and 70 and a subset of animals was used to evaluate the T-cell dependent antibody response (TDAR) to Keyhole limpet hemocyanin. Immune effects were more pronounced on PND 21 and 42 and observed at lower doses than developmental effects. The most sensitive immune parameters affected included TDAR parameters and thymocyte subpopulations with lower confidence limits of the benchmark doses (BMDLs) below the overall no-observed-adverse-effect-level (NOAEL) for DOTC reported so far in literature. These findings illustrate the relative sensitivity of the developing immune system for DOTC, the additional value of assessing functional immune parameters, and underscore the relevance of juvenile immunotoxicity testing in view of the risk assessment of chemicals.