Figure 2.

Inhibition of TRAF2 and NF-κB activity synergistically sensitizes thymocytes to TNF-induced apoptosis. (a) Thymocytes (2 × 10⁵/ well) from the indicated mice (6–8 wk old) were treated for 22 h with increasing amounts of murine TNF-α as indicated, and the percentages of cell death are shown as mean ± SD of triplicate samples from each group. Similar results were also obtained with human TNF-α (data not shown), which is specific for murine TNFR1. Representative data from one of five experiments are shown. Of note, the number and distribution of the major thymic subsets were normal, with the exception of a previously reported decrease in single positive cells in IκBα.DN-expressing mice and in double-TG mice expressing both TRAF2.DN and IκBα.DN (data not shown); however, this subset represented <1% of thymocytes in wild-type littermates. (b) Thymocytes from the indicated mice were treated overnight with TNF (33 ng/ml), with or without CHX (30 μg/ml), as indicated. Background cell death of thymocytes in medium ± CHX alone was ∼20–30%. Mean (± SD) data from one of three experiments, all of which yielded similar results, are shown.