Overexpression of Fas/CD95 and Fas-induced apoptosis in a patient with idiopathic CD4(+) T lymphocytopenia

The mechanisms of apoptosis have become better understood, in part with the discovery of Fas/CD95. We report the case of a patient characterized by a decreased CD4(+) T cell count and an overexpression of Fas/CD95 resulting i n apoptosis. A 54-year-old man presented with disseminated Mycobacterium xe nopi infection. Analysis showed CD4(+) T lymphopenia. Tests for human immun odeficiency virus (HIV) types 1 and 2 were negative. We compared the patien t with eight healthy controls and five HIV-infected patients in terms of th e expression of Fas/CD95 and Fas-mediated apoptosis of peripheral T lymphoc ytes. The percent of CD95(+) cells in lymphocytes was 98% for the patient, and the mean percent of CD95(+) cells in lymphocytes +/-SD for HIV-infected patients and healthy controls was 75% +/- 16% and 36% +/- 26%, respectivel y. The patient had a high level of spontaneous apoptosis, and apoptotic cel ls were all identified as being CD4(+) T cells. Monoclonal antibodies to CD 95 dramatically increased apoptosis of CD4(+) T cells exclusively. CD4(+) T lymphopenia observed in our patient correlated with an overexpression of F as together with spontaneous and Fas-induced apoptosis.