NF-κB in T lymphocyte development. A simplified schematic representation of T-lymphocyte development, highlighting some of the contributions of NF-κB at various developmental checkpoints. TReg and NKT cells branch off at some point after TCR expression on thymocytes. See text for details. DP, double-positive stage; DN3/DN4, double-negative stages; IKK, IκB kinase; NF-κB, nuclear factor-κB; NKT, natural killer T cell; SP, single-positive stage; TCR, T-cell receptor; TReg, T-regulatory cell.