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Alternate immune system targets for TCDD: lymphocyte stem cells and extrathymic T-cell development
A E Silverstone1, D E Frazier, T A Gasiewicz
1Department of Microbiology and Immunology, State University of New York Health Science Center, Syracuse 13210-2375.
Experimental and Clinical Immunogenetics
|January 1, 1994
Summary
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes thymic atrophy by damaging T-cell precursors outside the thymus. This process involves the AhR receptor and not apoptosis or estrogen receptors.
Area of Science:
- Immunology
- Toxicology
- Developmental Biology
Background:
- Thymic atrophy is a significant concern in toxicology.
- Extrathymic T-cell development is crucial for immune function.
Purpose of the Study:
- To investigate the mechanisms by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces thymic atrophy.
- To explore the role of extrathymic T-cell precursors in TCDD-mediated thymic atrophy.
Main Methods:
- Summarizing existing evidence on TCDD's effects on the immune system.
- Analyzing the involvement of specific receptors (AhR, estrogen receptor) and cellular mechanisms (apoptosis, bcl-2).
Main Results:
- TCDD-induced thymic atrophy is partly mediated by damage to extrathymic T-cell precursors in bone marrow and fetal liver.
- The bcl-2 proto-oncogene and apoptotic mechanisms are not involved in this atrophy.
- TCDD acts through its specific aryl hydrocarbon receptor (AhR), not the estrogen receptor.
- Both TCDD and estradiol promote extrathymic T-cell differentiation in the liver, including T-cells with V beta T-cell receptors normally deleted in the thymus.
Conclusions:
- TCDD-induced thymic atrophy involves extrathymic T-cell damage via the AhR.
- This pathway bypasses normal thymic deletion processes, potentially impacting immune repertoire diversity.