Decreased expression of Fas (APO‐1/CD95) on peripheral blood CD4+ T lymphocytes in cutaneous T‐cell lymphomas

BACKGROUND: The usually protracted and indolent course of cutaneous T-cell lymphoma (CTCL) is consistent with an accumulation of lymphocytes rather than being a true proliferative disorder, perhaps as the result of defective lymphocyte apoptosis. Fas (CD95) is the main signalling membrane molecule involved in postactivation T-lymphocyte apoptosis. OBJECTIVES: To evaluate expression of Fas on circulating CD4+ lymphocytes in patients with CTCL. METHODS: Fas expression on peripheral blood CD4+ T cells in 16 patients with mycosis fungoides (patch and infiltrated plaque stages) and in four patients with Sézary syndrome was compared with that in 25 matched patients with lymphocyte-mediated cutaneous benign inflammatory disorders and in 15 subjects without inflammatory cutaneous diseases. RESULTS: Fas expression on peripheral CD4+ lymphocytes was significantly lower in patients with CTCL compared with subjects with benign inflammatory cutaneous disorders and with healthy donors. CONCLUSIONS: This pattern supports the hypothesis that a defect in T-cell apoptosis may play a part in the pathophysiology of CTCL, perhaps through abnormalities of the Fas/Fas ligand system. Alternatively, this decrease could be the result of the presence of the soluble Fas ligand molecule in the sera of patients with CTCL.