CD4 and sarcoma: Most recently increased frequencies of CD4+CD25highFOXP3+ Treg cells were reported for patients with renal cell carcinoma, malignant melanoma or ovarian cancer patients after IL-2 monotherapy [37], [39], [40], [41] and administration of IL-2 during immune reconstitution after chemotherapy in pediatric sarcomas led to a preferential expansion of Treg cells after cytoreductive chemptherapy [38].