CD25 (4C9)

According to the World Health Organization classification system, the major diagnostic criterion for bone marrow involvement by Systemic Mastocytosis (SM) is the presence of dense aggregates (>15 cells) of mast cells. Expression of CD25, a low-affinity receptor for interleukin-2 (IL-2), is a reliable diagnostic tool for distinguishing neoplastic mast cell aggregates from reactive proliferations, and has therefore recently become a minor criterion for the diagnosis of SM. Hahn et al. demonstrated that aberrant staining of Mast cell clusters by anti-CD25 antibody in GI biopsies was essentially diagnostic of SM. Anti-CD25 antibody has also been useful in identifying mast cells in skin biopsies in the setting of Urticaria Pigmentosa, which is predictive of Systemic Mastocytosis. Quantitation of regulatory T cells (Treg) in the setting of hepatocellular carcinoma has been used as an independent predictive factor of tumor recurrence after hepatic resection for HCC. Also, the percentage of tumor-infiltrating CD25+FOXP3+ regulatory T cells among tumor cells, inside tumor parenchyma and at its periphery, is significantly higher in recurrent cutaneous melanoma than in non-recurrent melanoma.