Therefore, we believe that it is primarily the altered functional properties of the transgenic T cells that influence disease susceptibility in rats. Enhanced GR signaling has been hypothesized to alter the balance between Th1 and Th2 cytokines.20 This is now supported by our studies on EAE and allergic airway inflammation in rats. altered. Collectively, our findings suggest that endogenous glucocorticoids impact T-cell development and favor the selection of Th2- over Th1-dominated adaptive immune responses. Glucocorticoids (GCs) belong to a class of steroid hormones that are synthesized by the adrenal gland and released in response to stimuli such as stress and inflammation. Their secretion is usually under the control of the hypothalamus-pituitary-adrenal axis, a neuroendocrine cascade that involves positive and negative opinions loops. Once in the blood circulation, GCs exert pleiotropic effects ranging from the regulation of energy metabolism and the control of cognitive functions to the modulation of the immune system. Due to their lipophilic nature, they can passively diffuse into the cytoplasm and bind to the glucocorticoid receptor (GR). In turn, the GR translocates into the nucleus and interacts directly or indirectly via other transcription factors with promoter and enhancer elements of responsive genes.1,2 This ultimately prospects to altered gene expression, forming the basis for most of the immunomodulatory activities of GCs. Although application of pharmacological doses of synthetic GCs has strong anti-inflammatory and immunosuppressive effects, endogenous GCs seem to modulate rather than outright suppress the immune system.3,4 The role of the GR in these processes has been investigated in cell culture and animal models, implicating it in lymphocyte development, apoptosis, and the control of innate and adaptive immunity.5,6 Nevertheless, many aspects of the function that endogenous GCs play in the thymus and the modulation of immune responses remain controversial. In the thymus, immunocompetent T cells develop from pluripotent progenitors through a series of differentiation and selection actions.7 Whereas the ability of GCs to induce apoptosis in thymocytes is widely recognized, it is still controversial as to whether they are also involved in T-cell maturation.8,9 More than a decade ago, GR signaling was proposed to determine the outcome of positive and negative selection. Although mice expressing an antisense GR in the thymus were found to possess a T-cell repertoire with altered specificity, arguing that GC signaling impacts thymocyte selection, the analysis of hypomorphic GR knockout mice failed to provide Rabbit Polyclonal to RTCD1 any support for this model.10,11 Furthermore, there is also debate regarding the degree to which the thymus synthesizes GCs in addition to its common source, the adrenal gland.12 Corticosterone synthesis was demonstrated in the thymus,13,14,15 but studies using the inhibitor metyrapone led to ambiguous conclusions.16 Moreover, various functions were attributed to these GCs, ranging from T-cell development and thymic selection8,12 to the control of thymic involution.17 In summary, thymus-derived steroids and their relevance remain a matter of argument. Beyond a role in T-cell development, it is also believed that GCs impact the type of immune responses generated.18 In particular, it was observed that elevated levels of endogenous GCs, such as experienced during prolonged periods of stress, can suppress cellular immunity while boosting humoral immunity. This has led to the concept that GCs govern the outcome of autoimmune and atopic diseases via their influence on cytokine production.19,20 A link between the AM 580 activity of the hypothalamus-pituitary-adrenal axis and disease susceptibility is suggested by both animal experiments and human studies. Lewis rats, which have a hypoactive stress system, are extremely prone to the induction of Th1-mediated diseases such as experimental autoimmune encephalomyelitis.21,22 Conversely, women in the third trimester of pregnancy, who have increased levels of cortisol, often experience remission of Th1-mediated autoimmune diseases including multiple sclerosis and rheumatoid arthritis. 22 This was explained by increased production of IL-4 and IL-10 and a reduction in IL-12. In line with this notion, Th2-mediated autoimmune disorders such as systemic lupus erythematosus can flare up under conditions of chronically elevated cortisol levels.18 In summary, despite good evidence that the strength of GR signaling impacts autoimmune AM 580 and atopic diseases, the causal relationship to altered T-cell function is not yet well established. Although many studies AM 580 have resolved the question of what occurs when the GR is usually lacking, only a few reports have so far explored the physiological effects of increased GR levels Apoptosis Assay Total thymocytes or lymph node cells were cultured at 1 106 cells/ml RPMI made up of 10% charcoal/dextran-treated FCS (HyClone, Logan, UT) in 48-well plates for 24 hours as explained previously.32 The cells were analyzed by flow AM 580 cytometry using Annexin V and monoclonal antibodies against TCR, CD4, and CD8. Corticosterone RIA Blood.