IκB Kinase 2 Deficiency in T Cells Leads to Defects in Priming, B Cell Help, Germinal Center Reactions, and Homeostatic Expansion

Signal transduction from proinflammatory stimuli leading to NF-κB-dependent gene expression is mediated by the IκB kinase 2 (IKK2/IKKβ). Therefore, IKK2 has become an important drug target for treatment of inflammatory conditions. T cells, whose activation depends to a large extent on the activity of NF-κB transcription factors, play important roles in inflammation and autoimmunity. Ablation of IKK2 specifically in T cells in CD4cre/Ikk2FL mice allows their survival and activation by polyclonal stimuli in vitro, suggesting that IKK2 is dispensable for T cell activation. We report in this study that IKK2-deficient T cells expand efficiently in response to superantigen administration in vivo, but are completely deficient in recall responses, most likely due to inefficient priming. IKK2-deficient T cells provide suboptimal B cell help and fail to support germinal center reactions. Finally, IKK2 is essential for homeostatic expansion of naive T cells, reflected by the inability of IKK2-deficient T cells to induce colitis in lymphopenic hosts.