FKBP5 also kwnon as FKBP51, AIG6 is a member of the immunophilin protein family. FKBP5 plays a role in regulating T-cell activation and proliferation, primarily by inhibiting calcineurin phosphatase activity, which is essential for T-cell signaling. This inhibition is particularly important in immune responses, as FKBP5 helps modulate glucocorticoid effects and immunosuppressive drugs like FK506 and rapamycin. FKBP5 protein is predominantly expressed in T cells and is induced by glucocorticoids, making FKBP5 a significant player in immune system′s response to stress and inflammation. Additionally, FKBP5 protein′s interaction with other proteins, such as FKBP52, highlights FKBP5′s role in forming complexes that regulate steroid receptor activity, further emphasizing FKBP51′s importance in cellular signaling pathways.