Defective T cell activation and autoimmune disorder in Stra13-deficient mice.

Stra13, a basic helix-loop-helix transcription factor, is up-regulated upon activation of CD4+ T cells. Here we show that Stra13-deficient mice exhibit defects in several phases of CD4+ T cell activation. In vivo, Stra13 deficiency results in ineffective elimination of activated T and B cells, which accumulate progressively, leading to lymphoid organ hyperplasia. Consequently, aging Stra13-/- mice develop autoimmune disease characterized by accumulation of spontaneously activated T and B cells, circulating autoantibodies, infiltration of T and B lymphocytes in several organs and immune complex deposition in glomeruli. Our studies identify Stra13 as a key regulator of lymphocyte activation that is vital for maintenance of self-tolerance and for constraint of autoimmunity.