T cell homeostasis commonly refers to the maintenance of relatively stable T cell numbers in the peripheral lymphoid organs.Among the large numbers of T cells in the periphery,T cells exhibit structural diversity,i.e....T cell homeostasis commonly refers to the maintenance of relatively stable T cell numbers in the peripheral lymphoid organs.Among the large numbers of T cells in the periphery,T cells exhibit structural diversity,i.e.,the expression of a diverse repertoire of T cell receptors(TCRs),and functional diversity,i.e.,the presence of T cells at nave,effector,and memory developmental stages.Although the homeostasis of T cell numbers has been extensively studied,investigation of the mechanisms underlying the maintenance of structural and functional diversity of T ceils is still at an early stage.The fundamental feature throughout T cell development is the interaction between the TCR and either self or foreign peptides in association with MHC molecules.In this review,we present evidence showing that homeostasis of T cell number and diversity is mediated through competition for limiting resources. The number of T cells is maintained through competition for limiting cytokines,whereas the diversity of T cells is maintained by competition for self-peptide-MHC complexes.In other words,diversity of the self-peptide repertoire limits the structural(TCR)diversity of a T cell population.We speculate that cognate low affinity self-peptides, acting as weak agonists and antagonists,regulate the homeostasis of T cell diversity whereas non-cognate or null peptides which are extremely abundant for any given TCR,may contribute to the homeostasis of T cell number by providing survival signals.Moreover,self-peptides and cytokines may form specialized niches for the regulation of T cell homeostasis.Cellular & Molecular Immunology.2005;2(1):1-10.展开更多
文摘T cell homeostasis commonly refers to the maintenance of relatively stable T cell numbers in the peripheral lymphoid organs.Among the large numbers of T cells in the periphery,T cells exhibit structural diversity,i.e.,the expression of a diverse repertoire of T cell receptors(TCRs),and functional diversity,i.e.,the presence of T cells at nave,effector,and memory developmental stages.Although the homeostasis of T cell numbers has been extensively studied,investigation of the mechanisms underlying the maintenance of structural and functional diversity of T ceils is still at an early stage.The fundamental feature throughout T cell development is the interaction between the TCR and either self or foreign peptides in association with MHC molecules.In this review,we present evidence showing that homeostasis of T cell number and diversity is mediated through competition for limiting resources. The number of T cells is maintained through competition for limiting cytokines,whereas the diversity of T cells is maintained by competition for self-peptide-MHC complexes.In other words,diversity of the self-peptide repertoire limits the structural(TCR)diversity of a T cell population.We speculate that cognate low affinity self-peptides, acting as weak agonists and antagonists,regulate the homeostasis of T cell diversity whereas non-cognate or null peptides which are extremely abundant for any given TCR,may contribute to the homeostasis of T cell number by providing survival signals.Moreover,self-peptides and cytokines may form specialized niches for the regulation of T cell homeostasis.Cellular & Molecular Immunology.2005;2(1):1-10.
