Recent insights of T cell receptor-mediated signaling pathways for T cell activation and development.

T cell activation requires extracellular stimulatory signals that are mainly mediated by T cell receptor (TCR) complexes. The TCR recognizes antigens on major histocompatibility complex molecules with the cooperation of CD4 or CD8 coreceptors. After recognition, TCR-induced signaling cascades that propagate signals via various molecules and second messengers are induced. Consequently, many features of T cell-mediated immune responses are determined by these intracellular signaling cascades. Furthermore, differences in the magnitude of TCR signaling direct T cells toward distinct effector linages. Therefore, stringent regulation of T cell activation is crucial for T cell homeostasis and proper immune responses. Dysregulation of TCR signaling can result in anergy or autoimmunity. In this review, we summarize current knowledge on the pathways that govern how the TCR complex transmits signals into cells and the roles of effector molecules that are involved in these pathways. Researchers are unravelling the molecular signaling pathways that activate T cells, white blood cells which play a central role in the immune response. Sung-Gyoo Park and colleagues at the Gwangju Institute of Science and Technology in South Korea review the most recent insights and their significance for learning how to regulate the immune response in order to treat autoimmune disorders and other diseases. T cells are activated when a cluster of proteins on the cell surface, the T cell receptor complex, binds to molecules called antigens derived from pathogenic organisms or present on diseased cells. In autoimmune diseases, however, the receptor can be activated by the body’s own cells, initiating a damaging attack. Recent progress is identifying many specific molecules and their interactions in the cascades of signals that stimulate T cells following binding to antigens.