title: Mechanism of paroxysmal nocturnal hemoglobinuria clonal dominance: possible roles of different apoptosis and CD8+ lymphocytes in the selection of paroxysmal nocturnal hemoglobinuria clones.
abstract: OBJECTIVE
  Paroxysmal nocturnal hemoglobinuria (PNH), a clonal hematopoietic stem cell disorder, manifests when the PNH clone populates in the hematopoietic compartment. We explored the roles of different apoptosis of GPI+ and GPI- (glycosylphosphatidylinositol) cells and CD8+ lymphocytes in a selection of PNH clones.
  
  
  METHODS
  Granulocytes from PNH patients and normal controls were subjected to an apoptosis assay using annexin V. Hematopoietic cell in semisolid media were cultured with or without CD8+ lymphocytes.
  
  
  RESULTS
  In PNH, CD59+ granulocytes exhibited more apoptosis than their CD59- counterparts, after 0 or 4 hours in liquid growth culture system (mean [standard error of mean]: 2.1 (0.5) vs 1.2 (0.2), P=.01 at 0 hour and 3.4 [0.7] vs 1.8 [0.3], P=.03 at 4 hour, respectively). The presence of mononuclear cells (MNCs) rendered a greater difference in apoptosis. The percentages of apoptotic CD59+ granulocytes measured at 4 hours with or without MNC fraction were correlated with the sizes of PNH clones (r=0.633, P=.011; and r=0.648, P=.009; respectively). The autologous CD8+ lymphocytes inhibited CFU-GM and BFU-E colony formation in PNH patients when compared with normal controls (mean [SEM] of percentages of inhibition: 61.7 (10.4) vs 11.9 (2.0), P=.008 for CFU-GM and 26.1 (6.9) vs 4.9 (1.0), P=.037 for BFU-E).
  
  
  CONCLUSIONS
  Increased apoptosis of GPI+ blood cells is likely to be responsible in selection and expansion of PNH clones. MNCs or possibly CD8+ lymphocytes may play a role in this phenomenon.
authors.affiliation: Division of Hematology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: Rajita
authors.initials: R
authors.lastname: Kunyaboon
authors.forename: Wanchai
authors.initials: W
authors.lastname: Wanachiwanawin
authors.forename: Yaowalak
authors.initials: Y
authors.lastname: U-Pratya
authors.forename: Anchalee
authors.initials: A
authors.lastname: Thedsawad
authors.forename: Orathai
authors.initials: O
authors.lastname: Taka
mesh_terms: D000328:Adult; D000368:Aged; D017209:Apoptosis; D018957:CD59 Antigens / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology* / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006098:Granulocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D006457:Hemoglobinuria, Paroxysmal / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008297:Male; D008875:Middle Aged
chemical_list: D018957:CD59 Antigens; D017261:Glycosylphosphatidylinositols