Journal
ARCHIVES OF TOXICOLOGY
Volume 76, Issue 10, Pages 570-580Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s00204-002-0390-2
Keywords
2,3,7,8-tetrachlorodibenzo-p-dioxin (TODD); T cell activation; superantigen; apoptosis; Fas
Categories
Funding
- NIDA NIH HHS [DA014885] Funding Source: Medline
- NIEHS NIH HHS [F31ES11562, ES09098] Funding Source: Medline
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Immune response against a foreign antigen is characterized by a growth phase, in which antigen-specific T cells clonally expand, followed by a decline phase in which the activated T cells undergo apoptosis, a process termed activation-induced cell death (AICD). In the current study, we have investigated the phase at which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) acts to downregulate the antigen-specific T cell response. To this end, C57BL/6 +/+ mice were injected with staphylococcal enterotoxin A (SEA) into the footpads (10 mug/footpad), and simultaneously treated with TCDD (10 or 50 mug/kg intraperitoneally). At various time points, the draining lymph node (LN) cells were analyzed for SEA-activated T cells. The data demonstrated that in C57BL/6 +/+ mice, TCDD treatment did not alter the growth phase but facilitated the decline phase of SEA-reactive T cells. TCDD caused a significant decrease in the percentage and absolute numbers of CD4(+) and CD8(+) SEA-responsive T cells expressing Vbeta3(+) and Vbeta11(+) but did not affect SEA-nonresponsive Vbeta8(+) T cells. Upon in vitro culture, TCDD-exposed SEA-immunized LN cells exhibited increased levels of apoptosis when compared with the vehicle controls. When Fas-deficient (C57BL/6 lpr/lpr) or Fas ligand defective (C57BL/6 gld/gld) mice were treated with TCDD, they failed to exhibit a decrease in percentage and cellularity of SEA-reactive T cells, thereby suggesting a role of Fas-Fas ligand inter-actions in the TODD-induced downregulation of SEA-reactive T cell response. The resistance to TCDD-induced decrease in T cell responsiveness to SEA seen in Fas- and FasL-mutant mice was neither due to decreased aryl hydrocabon receptor (AhR) expression nor to altered T cell responsiveness to SEA. The current study demonstrates that TCDD does not prevent T cell activation, but prematurely induces Fas-based AICD, which may contribute to the deletion of antigen-primed T cells.
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