TNF blockade rescues SP development in IKKΔT^CD4 mice. (A and B) Ikk1^fx/fx Ikk2^fx/fx R26^REYFP CD4^Cre (IKKΔT^CD4) mice (8–16 wk old) were treated with anti-TNF mAb i.p. (1 mg/inject; n = 16) or PBS as control (n = 17). After 7 d, thymus and lymph node cells were analyzed by FACS. (A) Density plots are of TCR versus HSA expression by CD4SP (top row) and CD8 SP (bottom row) from IKKΔT^CD4 mice treated with anti-TNF or PBS as compared with untreated Cre -ve littermate controls (Cre^–, n = 17). Bar charts show total cell recoveries of HSA^hi and HSA^lo cells among CD4SP (top row) and CD8SP (bottom row). (B) Density plots are of CD44 versus CD25 by CD4⁺TCR^hi T cells (top row) and CD44 versus TCR by CD8⁺ cells from lymph nodes of the same treatment groups described in A. Bar charts show cell numbers of naive CD4 (top chart) and naive CD8 (bottom chart) T cells from mice. (C) Density plots are of CD4 versus CD8 by total live thymocytes (top row), and TCR versus HSA by CD4SP (middle row) and CD8SP thymocytes (bottom row) from IKKΔT^CD4 mice, Cre -ve littermate controls (Cre^–), Tnfrsf1a^−/− IKKΔT^CD4 mice (n = 16), and Cre -ve littermate controls (Tnfrsf1a^−/− Cre^–, n = 13). (D) Bar charts show cell numbers of the indicated SP subset recovered from IKKΔT^CD4 mice treated with anti-TNF (αTNF) or PBS as described in A, untreated Cre -ve littermates (Cre^–), or Tnfrsf1a^−/− IKKΔT^CD4 mice and Cre -ve littermate controls (Tnfrsf1a^−/− Cre^–). (E) Bar charts show total numbers of naive CD44^lo CD25^– CD4⁺ TCR^hi T cells and naive CD44^lo CD8⁺ TCR^hi T cells from lymph nodes of Ikk1^fx/fx Ikk2^fx/fx R26^REYFP CD4^Cre (IKKΔT^CD4, n = 17) mice, Cre -ve littermates (Cre^–, n = 17), Tnfrsf1a^−/− IKKΔT^CD4 mice (n = 16), and Cre -ve littermate (Cre– Tnfrsf1a^−/−, n = 13) as control. Histograms are of IL-7Rα by gated naive CD44^lo CD25^– CD4⁺ TCR^hi T cells (top) and naive CD44^lo CD8⁺ TCR^hi T cells (bottom) from WT (black broken lines), Tnfrsf1a^−/− IKKΔT^CD4 mice (red solid lines) and Cre -ve Tnfrsf1a^−/− littermates (solid line). Gray fills are IL-7Rα expression by DP thymocytes from WT mice as negative control. FACS data are representative of four or more independent experiments, and bar charts are pooled from four or more independent experiments. ****, P < 0.0001.