title: T cells expressing the activating NK-cell receptors KIR2DS4, NKG2C and NKG2D are elevated in paroxysmal nocturnal hemoglobinuria and cytotoxic toward hematopoietic progenitor cell lines.
abstract: OBJECTIVE
  To investigate the presence of T cells with natural killer cell receptors (NKR) in paroxysmal nocturnal hemoglobinuria (PNH), and their potential involvement in clonal expansion of glycosylphosphatidylinositol (GPI)-deficient hematopoietic stem cells by selective immune attack to normal and not GPI-deficient hematopoietic stem cells.
  
  
  METHODS
  By flow cytometry, the frequency and number of T cells expressing NKR was evaluated in 39 PNH patients and compared to healthy controls. Elevated T cell subsets in PNH were assessed for differential cytotoxic lysis of GPI(+) and GPI(-) CD34(+) hematopoietic progenitor cell lines.
  
  
  RESULTS
  In PNH patients, the frequency (p < 0.001) and absolute number of T cells expressing the NKR CD56 (p = 0.01) were significantly increased. Furthermore, a higher percentage of T cells expressed the activating NKR NKG2D (p < 0.01), NKG2C (p < 0.01), and KIR2DS4 (p = 0.01). Further characterization showed that these populations predominantly consist of CD8(+) effector memory CD45RA(+) T cells (T(EMRA)). NKR(+) cytotoxic T-lymphocyte lines isolated from PNH patient peripheral blood and bone marrow displayed high cytotoxicity towards CD34(+) hematopoietic progenitor cell lines and K562 cells, suggesting major histocompatibility complex class I-independent cytotoxicity. These cytotoxic T lymphocyte (CTL) lines are capable of differential lysis of GPI(+) and GPI(-) hematopoietic cell lines, however, not in all cases. This suggests that multiple factors, such as the highly activated status of in vitro cultured CTLs, influence whether GPI-dependent lysis occurs.
  
  
  CONCLUSIONS
  The increased frequency of CD8(+) effector-memory T cells with activating NKR and cytotoxicity toward hematopoietic cell lines suggests involvement in bone marrow failure and clonal expansion in PNH.
authors.affiliation: Department of Hematology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Sandra T A
authors.initials: ST
authors.lastname: van Bijnen
authors.forename: Marian
authors.initials: M
authors.lastname: Withaar
authors.forename: Frank
authors.initials: F
authors.lastname: Preijers
authors.forename: Arnold
authors.initials: A
authors.lastname: van der Meer
authors.forename: Theo
authors.initials: T
authors.lastname: de Witte
authors.forename: Petra
authors.initials: P
authors.lastname: Muus
authors.forename: Harry
authors.initials: H
authors.lastname: Dolstra
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006412:Hematopoietic Stem Cells / Q000276:immunology* / Q000378:metabolism; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology; D020014:K562 Cells; D008297:Male; D008875:Middle Aged; D055654:NK Cell Lectin-Like Receptor Subfamily C / Q000276:immunology* / Q000378:metabolism; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000276:immunology* / Q000378:metabolism; D054340:Receptors, KIR / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D055815:Young Adult
chemical_list: D017261:Glycosylphosphatidylinositols; C473953:KIR2DS4 protein, human; C527059:KLRC2 protein, human; C527085:KLRK1 protein, human; D055654:NK Cell Lectin-Like Receptor Subfamily C; D055655:NK Cell Lectin-Like Receptor Subfamily K; D054340:Receptors, KIR