デキサメタゾン誘導性の胸腺退縮における未熟胸腺T細胞の分極化

抄録

Thymus is a primary lymphoid organ important for cellular immune response. The size and function of thymus is rapidly shrunken by various biological and environmental stimulation, which is called as thymic atrophy or thymic involution, to increase risks of infectious diseases and tumorigenesis. In the healthy thymus, naïve T cells have some characters like Th1- or Th2-differentiated T cells. This bias of naïve T cell characters, called as polarization, is tentative and could be changed during thymic involution. Indeed, naïve T cells are more polarized to Th2 than Th1 during dietary restriction-induced thymic involution (Razali et al., in press). We here examined how the polarization of naïve T cells is affected during glucocorticoid-induced thymic involution. ICR mice were administered dexamethasone and their thymus was analyzed. The results indicated that naïve T cells were more polarized to Th2 by dexamethasone, like by the dietary restriction. However, the induction of some Th2 markers was not equivalent under these two stresses, indicating different characters of polarized naïve T cells. In contrast to the dietary restriction, the dexamethasone-administration did not up-regulate the expression of synthetic enzymes of prostanoids, suggesting that prostanoids are not critical mediators of glucocorticoid-induced thymic involution.