ApoptosisplaysanessentialroleinTcellbiology.ThymocytesexpressingnonfunctionalorautoreactiveTCRsareeliminatedbyapoptosisduringdevelopment.ApoptosisalsoleadstothedeletionofexpandedeffectorTcellsduringimmuneresponses.Thedysregulationofapoptosisintheimmunesystemresultsinautoimmunity,tumorogenesisandimmunodeficiency.Twomajorpathwaysleadtoapoptosis:theintrinsiccelldeathpathwaycontrolledbyBcl-2familymembersandtheextrinsiccelldeathpathwaycontrolledbydeathreceptorsignaling.Thesetwopathwaysworktogethertoregu