Persistent suppression of contact hypersensitivity, and altered T-cell parameters in F344 rats exposed perinatally to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD)

The outcome of perinatal low-level TCDD exposure on the T-cell-mediated contact hypersensitivity (CHS) response in adult F344 rats was investigated. Suppression of the 2,4-dinitrofluorobenzene (DNFB)-specific contact hypersensitivity reponse occurred in mature offspring of dams dosed by gavage with 1 μg or 3 μg TCDD/kg on gestation day (GD) 14. To determine if this effect was correlated with altered distribution or activation of major T-cell subtypes, cells of the auricular lymph node draining the hapten-treated skin were evaluated by flow cytometry for expressed phenotype, including activation markers, 24 h after challenge. Six-month-old female offspring with significantly decreased CHS and born to dams given 3 μg TCDD/kg, had significantly greater proportion of CD4 + T cells expressing a naive phenotype marker, CD45RC hi, in their draining nodes. The greater relative frequency of this CD4 + subset in peripheral lymphoid tissues associated with a reduced CHS in these rats may be attributed to a reduction in the proportion of CD4 + T cells maintaining or recruited into an activated state. The CHS proved to be a valuable bioassay for investigating long-term immunotoxic effects of perinatal TCDD exposure in rats.