title: MICA polymorphism identified by whole genome array associated with NKG2D-mediated cytotoxicity in T-cell large granular lymphocyte leukemia.
abstract: BACKGROUND
  Large granular lymphocyte leukemia is a semi-autonomous clonal proliferation of cytotoxic T cells accompanied by immune cytopenias and various autoimmune conditions. Due to the rarity of this disease and its association with autoimmune diseases, a theoretical germline or somatic mutation might have significant penetrance, thus enabling detection, even from samples of suboptimal size, through genome-wide association studies.
  
  
  METHODS
  To investigate a non-mendelian genetic predisposition to large granular lymphocyte leukemia, we used a step-wise method for gene discovery. First, a modified 'random forests' technique was used for candidate gene identification: this was followed by traditional allele-specific polymerase chain reaction, sequencing modalities, and mechanistic assays.
  
  
  RESULTS
  Our analysis found an association with MICA, a non-peptide-presenting, tightly regulated, stress-induced MHC-like molecule and cognate receptor for NKG2D, found abundantly on large granular lymphocyte leukemia cells. Sequencing of germline DNA revealed a higher frequency of MICA*00801/A5.1 in patients with large granular lymphocyte leukemia than in matched controls (64% versus 41%, P<0.001, homozygous 40% versus 15%, P<0.001). Flow cytometry was employed to determine the expression of MICA within hematologic compartments, showing that the signal intensity of MICA was increased in granulocytes from neutropenic patients with large granular lymphocyte leukemia in comparison with that in controls (P=0.033). Furthermore, neutrophil counts were inversely correlated with MICA expression (R(2)=0.50, P=0.035). Finally, large granular lymphocyte leukemia cells were able to selectively kill MICA(+) Ba/F3 lymphocytes transfected with human MICA*019 in a dose-dependent manner compared to naïve cells (P<0.001), an effect mitigated by administration of an anti-NKG2D antibody (P=0.033).
  
  
  CONCLUSIONS
  Our results illustrate that MICA-NKG2D played a role in disease pathogenesis in the majority of patients in our cohort of cases of large granular lymphocyte leukemia and further investigation into this signaling axis may provide potent therapeutic targets.
authors.affiliation: Department of Translational Hematologic and Oncologic Research, Taussig Cancer Center R/40, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio, USA.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Viny
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Clemente
authors.forename: Monika
authors.initials: M
authors.lastname: Jasek
authors.forename: Medhat
authors.initials: M
authors.lastname: Askar
authors.forename: Hemant
authors.initials: H
authors.lastname: Ishwaran
authors.forename: Amy
authors.initials: A
authors.lastname: Nowacki
authors.forename: Aiwen
authors.initials: A
authors.lastname: Zhang
authors.forename: Jaroslaw P
authors.initials: JP
authors.lastname: Maciejewski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003602:Cytotoxicity, Immunologic; D005260:Female; D020022:Genetic Predisposition to Disease; D055106:Genome-Wide Association Study; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D054066:Leukemia, Large Granular Lymphocytic / Q000209:etiology* / Q000235:genetics / Q000276:immunology; D008297:Male; D008875:Middle Aged; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000235:genetics*; D011110:Polymorphism, Genetic
chemical_list: D015395:Histocompatibility Antigens Class I; C527085:KLRK1 protein, human; C099187:MHC class I-related chain A; D055655:NK Cell Lectin-Like Receptor Subfamily K
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