title: Delayed activation-induced T lymphocytes death in aplastic anemia: related with abnormal Fas system.
abstract: OBJECTIVE
  To quantitate apoptosis and Fas antigen expression of T lymphocytes by activation in aplastic anemia (AA) and compare with that of normal controls and completely-recovered AA, and to investigate the apoptotic sensitivity to anti-fas antibody of activated T lymphocytes in AA.
  
  
  METHODS
  We studied the expression of Fas antigen on fresh T lymphocytes of twenty patients with AA [13 newly diagnosed, 7 recorvered AA after immunosuppressive therapy (IST)], and investigated the activation-induced cell death (AICD) and Fas expression by activation [interleukin-2 (200 U/ml) and phytohemagglutinin (50 micrograms/ml)] in 5 newly-diagnosed AA, 5 normal controls and 5 AA in complete response (CR). Apoptotic sensitivity to anti-Fas antibody was assessed by the time-course kinetics of induction of cell death by anti-Fas antibody (500 ng/ml).
  
  
  RESULTS
  There was no significant difference of Fas antigen expression on freshly-isolated T lymphocytes among newly-diagnosed severe AA, normal controls and patients with AA in CR after IST. In normal controls, T lymphocytes death was greatly increased at 3 days of activation, and Fas antigen expression on T lymphocytes was increased above baseline at day 1 of activation. In contrast, in newly-diagnosed AA, T lymphocytes showed delayed cell death, which correlated with a slowed increase of Fas antigen expression by activation. Also, anti-Fas antibody sensitivity of activated T lymphocytes was decreased in newly-diagnosed AA. In completely recovered AA, these abnormal AICD and Fas antigen expressions by activation were recovered to normal range.
  
  
  CONCLUSIONS
  Abnormal AICD plays a role in the immune pathophysiology of AA, and defective Fas system is involved in this process.
authors.affiliation: Department of Internal Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: S C
authors.initials: SC
authors.lastname: Kim
authors.forename: Y H
authors.initials: YH
authors.lastname: Min
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: S Y
authors.initials: SY
authors.lastname: Chung
authors.forename: N C
authors.initials: NC
authors.lastname: Yoo
authors.forename: J W
authors.initials: JW
authors.lastname: Lee
authors.forename: J S
authors.initials: JS
authors.lastname: Hahn
authors.forename: Y W
authors.initials: YW
authors.lastname: Ko
mesh_terms: D000741:Anemia, Aplastic / Q000276:immunology* / Q000473:pathology; D017209:Apoptosis; D016022:Case-Control Studies; D006801:Humans; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology* / Q000473:pathology*; D013997:Time Factors; D019014:fas Receptor / Q000097:blood
chemical_list: D019014:fas Receptor