CD25 is the alpha chain of the IL-2 receptor. It
is a Type I transmembrane protein present on
activated T-cells, activated B-cells, some
thymocytes, myeloid precursors, and oligodendrocytes
that associates with CD122 to form
a heterodimer that can act as a high-affinity
receptor for IL-2. It is expressed in most B-cell
neoplasms, some Acute Non-lymphocytic
Leukemias, and Neuroblastomas.
Expression of CD25 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 Systemic Mastocytosis (SM). Anti-CD25
antibodies have 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 for 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 are significantly
higher in recurrent Cutaneous Melanoma than in
Non-recurrent Melanoma.