Deletion or mutation of RelB [12], the tumor necrosis factor receptor-associated factor 6 (Traf6) [13], NFκB-inducing kinase (NIK) [14] and the lymphotoxin β receptor (LTβR) [15], leads to defective development of mTECs, reduced or absent medulla and development of autoimmunity [16], [17]. The gene discussed is LTBR; the disease is Autoimmunity.