NO EVIDENCE FOR EMERGENCE OF AUTOREACTIVE V-BETA-6(-CELLS IN MLS-1(A)MICE FOLLOWING EXPOSURE TO A THYMOTOXIC DOSE OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN() T)

Tolerance to minor lymphocyte stimulatory-1(a) (Mls-1(a)) antigens is associated with clonal deletion of cells carrying the T cell recpetor variable region V beta 6. Thymic epithelial cells may contribute to th e intrathymic negative selection of potentially autoreactive V beta 6( +) cells, Because 2,3,7,X-tetrachlorodibenzo-p-dioxin (TCDD) acts on t hymic epithelial cells, we hypothesized that it may interfere with int rathymic selection processes. In the present study, this was addressed by exposing Mls-1(a) DBA/2 mice to a single thymotoxic dose of TCDD, The emergence of V beta 6(+) cells in thymus, spleen, and mesenteric l ymph nodes was investigated during the subsequent recovery of TCDD-ind uced thymic atrophy. In addition, the extrathymic differentiation of T lym phocytes in the liver was studied. TCDD exposure resulted in a se vere thymic atrophy, and an increase in hepatic mononuclear tiated eit her intrathymically or extrathymically, in TCDD-exposed DBA/2 mice.