severe autoimmunity resembling Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX) syndrome, caused by mutations in FOXP3 gene. CD25 as a biomarker Levels of CD25 soluble form, called sIL-2Rα, has been connected to pathogenesis of autoimmune diseases and cancer. Since sCD25 is produced during immune activation, it is used as one of biomarkers to track disease progression and to indicate outcome for clinical disorders. Especially, it is a hallmark for hyper-activated immune system and cytokine storm, which may lead to multiple organ system failure. In cancer, increased levels of this soluble protein are diagnostic marker for leukemia and lymphoma. Furthermore, sIL-2Rα levels have some significance also in infectious diseases and transplantation. Higher serum levels were correlated with severity and need for hospitalisation of COVID-19 patients. sIL-2Rα amount in plasma of HIV ( human immunodeficiency virus) positive patients has a correlation to HIV viral load and so to disease progression. Similarly in Chagas disease, caused by the protozoan Trypanosoma cruzi, patients have increased levels of sIL-2Rα and autoantibodies. In regard to transplantation, higher levels of sCD25 may be used as a predictor of organ rejection and graft-versus-host disease (GVHD) for hematopoietic transplantations. Concerning CVD (cardiovascular diseases) soluble IL-2Rα has positive correlation with hypertension, type 2 diabetes mellitus, cardiac sarcoidosis, stroke and heart failure. For neurological disorders, high levels of sIL-2Rα are a sign for increased risk of developing schizophrenia. CD25 as a therapeutic target Since Tregs express IL-2Rα subunit constitutively on the surface, some immunotherapeutic approaches try to use this information for selectivity. NARA1 antibody is used in antitumour approaches to preferentially supplement Interleukin-2 to conventional CD8+ T cells . NARA1 binds to the cytokine on the IL-2Rα binding side preventing binding to CD25. This complex should therefore interact with conventional T lymphocytes over T regulatory cells and thus increase cytotoxic activity without increasing suppressing activity in tumour environment. Antibodies directly against CD25 have been altered to contain ‘activating’ Fc regions for the purpose of antibody-dependent cell-mediated cytotoxicity, in this case Treg depletion. Antibody marks a cell with IL-2Rα subunit on the surface, which is subsequently recognized and cleared by myeloid cell with Fc receptor. Moreover, for treatment of multiple sclerosis, drug called daclizumab binds to IL2RA and so blocks high-affinity IL-2 receptors on recently activated T cells for interaction with IL-2 as well as IL-2 cross-presentation by dendritic cells. From the other side, treatment strategies for autoimmune and inflammatory diseases need selectivity