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.