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 in apoptosis. A 54-year-old man presented with disseminated Mycobacterium xenopi infection. Analysis showed CD4+ T lymphopenia. Tests for human immunodeficiency virus (HIV) types 1 and 2 were negative. We compared the patient with eight healthy controls and five HIV-infected patients in terms of the expression of Fas/CD95 and Fas-mediated apoptosis of peripheral T lymphocytes. 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%, respectively. The patient had a high level of spontaneous apoptosis, and apoptotic cells were all identified as being CD4+ T cells. Monoclonal antibodies to CD95 dramatically increased apoptosis of CD4+ T cells exclusively. CD4+ T lymphopenia observed in our patient correlated with an overexpression of Fas together with spontaneous and Fas-induced apoptosis.