title: Genetic diversity of KELnull and KELel: a nationwide Austrian survey.
abstract: BACKGROUND
  Besides ABO and RH, the KEL blood group system, including the two antithetical antigens KEL1 and KEL2, is the most important owing to the frequent appearance of anti-KEL alloantibodies and their considerable clinical significance. So far, only limited information was available on KEL variant alleles determining the rare silent KELnull and KELel phenotypes with absent or diminished KEL antigen expression detected only by adsorption-elution techniques, respectively.
  
  
  METHODS
  For a systematic investigation of the KELnull and KELel phenotypes, 401 KEL:1,-2 samples (representing 2.6% of all Austrian KEL:1,-2 samples) and 811 KEL:1,2 samples were genotyped for the KEL*1/KEL*2-specific single-nucleotide polymorphism. All heterozygous KEL*1/KEL*2 and 4 additional KELnull samples were subjected to detailed immunohematologic examination and allele-specific sequencing.
  
  
  RESULTS
  In 14 KEL:1,-2 samples, discrepant KEL*1/KEL*2 heterozygosity was observed, indicating the presence of silent or barely expressed KEL*2 alleles, whereas all KEL:1,2 individuals were homozygous for KEL*2. In the course of further molecular analysis, 8 novel KEL*2null and 2 KEL*2el alleles were discovered, representing 67 and 33 percent of previously known KEL*2null- and KEL*2el-encoding alleles, respectively. In addition, two different known KEL*2null and KEL*2el alleles each were confirmed. The immunohematologic properties of KEL variant red blood cells were defined by extended KEL phenotyping and flow cytometric KEL1, KEL2, KEL4, and KEL7 antigen as well as total Kell protein quantification.
  
  
  CONCLUSIONS
  For the first time, exact KELnull and KELel population frequencies could be established in this population.
authors: Department of Blood Group Serology and Transfusion Medicine, Medical University of Vienna, Vienna, Austria.
authors: Günther F
authors: GF
authors: Körmöczi
authors: Thomas
authors: T
authors: Wagner
authors: Christof
authors: C
authors: Jungbauer
authors: Maria
authors: M
authors: Vadon
authors: Norbert
authors: N
authors: Ahrens
authors: Willi
authors: W
authors: Moll
authors: Annelies
authors: A
authors: Mühlbacher
authors: Seyhan
authors: S
authors: Ozgül-Gülce
authors: Thomas
authors: T
authors: Kleinrath
authors: Susanne
authors: S
authors: Kilga-Nogler
authors: Diether
authors: D
authors: Schönitzer
authors: Christoph
authors: C
authors: Gassner
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001317:Austria; D001483:Base Sequence; D001782:Blood Donors; D004252:DNA Mutational Analysis; D004912:Erythrocytes / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D005787:Gene Frequency; D018740:Genetic Heterogeneity; D014644:Genetic Variation; D005838:Genotype; D005843:Geography; D006801:Humans; D007626:Kell Blood-Group System / Q000235:genetics* / Q000276:immunology; D008969:Molecular Sequence Data; D010641:Phenotype; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
chemical_list: D007626:Kell Blood-Group System