Regulation of pre-T-cell development

One important pillar of cellular immune defense in mammals is the T-lymphoi d compartment which produces cells that are able to specifically recognize foreign peptide antigens through a membrane-bound receptor. These T-cells c an trigger a variety of defense mechanisms upon antigen stimulation ranging from the production of potent cytokines to the direct killing of virus-inf ected cells. The production of such highly specialized T-cells takes place in the thymus and requires a stringent process of differentiation and selec tion of precursor cells that are delivered from the bone marrow. In the thy mus, several waves of proliferative expansion and selection ensure the prod uction of a large repertoire of antigen-specific T-cells that each bear a u nique T-cell receptor (TCR) which is able to recognize foreign antigens but can tolerate the own host-specific peptide structures. Education of precur sors to mature T-cells in the thymus requires a dense network of regulatory processes acting at receptor-ligand interactions, signal transduction, gen omic rearrangement of TCR gene loci, cell cycle progression, transcriptiona l control and programmed cell death.