Role of glutathione and reactive oxygen intermediates in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced immune suppression in C57BI/6 mice

Recent developments in basic immunology have revealed the importance of glu tathione (GSH) and cellular redox balance in the generation of an immune re sponse. In the liver, it has been shown that exposure to 2,3,7,8-tetrachlor odibenzo-p-diomin (TCDD) al ters cellular GSH and reactive oxygen intermedi ate (ROI) production. We have tested the hypothesis that TCDD mediates the suppression of the cytotoxic T lymphocyte (CTL) response to alloantigen by increasing oxidative stress. Total cellular GSH, GSSG, and GSH-protein addu cts were analyzed by HPLC. Changes in intracellular GSH and ROI were simult aneously measured in isolated hepatocytes and individual subpopulations of spleen cells (CD4(+), CD8(+), B220(+), and Mac-1(+)) following in mpo expos ure to TCDD and antigenic challenge with P815 mastocytoma cells. Monochloro bimane was utilized to measure GSH levels, and two fluorescent probes were used to evaluate ROI levels: dichlorofluoroscein diacetate to monitor perox ides and dihydroethidine to assess superoxide anion. In hepatocytes, in viv o treatment with TCDD resulted in a transient, 2-fold increase in GSH, a 50 % decrease in peroxide levels and a small (20-40%) decrease in superoxide a nion levels. Although alloantigen challenge resulted in increased GSN and p eroxide in spleen cells, in vivo exposure to TCDD had no effect on splenic ROI levels, nor did it consistently alter GSH levels in any subpopulation o f spleen cells examined. Moreover, in vivo treatment with the antioxidant N -acetyl cysteine failed to affect the immune suppression caused by TCDD. Th ese results suggest to us that although TCDD perturbs cellular redox balanc e in the liver, it does not exacerbate or diminish the normal increased GSH and ROI which occur in the spleen in response to antigenic challenge.