In recent years, the concept that CD4+ T cells are divided into Th1 and Th2 subpopulations has been constantly updated with the continuous improvement in technology. CD4+T can differentiate into Th1, Th2, Treg, Th17, Th9, and Th22 subpopulations with different immunologic functions in vivo. Th17 mainly secretes IL-17, whereas Th9 cell mainly secretes IL-9 and IL-10. Furthermore, IL-22 is the main effector for Th22 cell-realizing immunoregulation. During stimulus or alien antigen attack, the function of either Th1 or Th2 subpopulation is increased, whereas that of other subpopulations is reduced, causing Th1-Th2 disequilibrium or the so-called “immunologic drift” phenomenon. In that way, which immunologic drift changes are hippocampus Th cells of chronic Immobilization stress rats in this study subject to? In the above analysis, we discussed the down-regulation of CCL5 or monocyte chemoattractant protein-1 expression during the 7-day and 21-day stress processes. Chiu et al. revealed that the expression of MCP-1 is Niraparib PARP inhibitor up-regulated in the Th1dominant response state but down-regulated in the Th2-dominant response state. Therefore, the 7-day and 21-day stresses down-regulate hippocampal Th1 cell-mediated cellular immunologic response and up-regulate Th2 cell-mediated immunologic response. In addition, IL-13RA2 expression is up-regulated and interleukin 22 receptor, alpha 2 expression is down-regulated in the 7-day stress. IL-9R and IL-22RA2 expressions are down-regulated and IL-17RB expression is up-regulated in the 21-day stress. The up-regulation or down-regulation of the expressions of IL-13RA2, IL-22RA2, IL-9R, and IL-17RB receptors indicates that the corresponding IL-9, IL-22, IL-13, and IL-17 expressions in the hippocampal tissue of the stressed rats are either inhibited or activated. Therefore, the above analysis of Th cell classification clearly implies that the disequilibrium of hippocampal Th cells Th1/ Th2 occurs in the 7-day and 21-day stress Kinase Inhibitor Library in vivo processes and that Th1 and Th2 chemotactically drift towards Th2 to inhibit the immunologic function of Th22 cells. The 21-day stress continuously inhibits the immunologic function of Th9 cells but enhances the immunologic function Th17 cells. Furthermore, the expression of STAT6 is up-regulated in the 7-day stress, whereas that of STAT4 is down-regulated in the 21-day stress. Therefore, Th cells are speculated to drift towards Th2 more significantly in the 7-day stress than in the 21-day stress, whereas the 21-day stress inhibits Th1 cell more significantly than the 7-day stress. In addition, during the 21-day stress, IL-22RA2 and IL-17RB show opposite expressions. Moreover, IL-22RA2 expression is down-regulated more significantly in the 7-day stress than in the 21day stress. Therefore, this study speculates that IL22RA2 mainly resulted from Th22 cell expression rather than from Th1 and Th17 cell expressions. We have continuously clarified the immunologic drift phenomenon of hippocampus Th cells in stressed rats. The most fundamental reason for the immunologic drift has yet to be determined. Previous studies suggest that the effects of stress on the body are mainly caused by increased endogenous GC, due to stress reaction or exogenous GC for clinical treatment. The changes in the intracorporeal GC level that cause abnormal cytokine expression, thereby resulting in cytokine balance network disorder and various diseases.