title: Identification of novel silent KEL alleles causing KEL:-5 (Ko) phenotype or discordance between KEL:1,-2 phenotype/KEL*01/02 genotype.
abstract: BACKGROUND
  The Kell system, encoded by the KEL gene, is one of the most clinically important blood group systems. Molecular defects may lead to the absence of Kell antigen expression. The very rare KEL:5 results from silent KEL genes, also called KELnull alleles. In a few cases, the rare KEL:1,-2 phenotype may be associated with silent KEL*02 alleles.
  
  
  METHODS
  The aim of this study was to perform DNA investigations to identify silent KEL alleles among 10 KEL:-5 patients and 121 individuals presenting the rare KEL:1,-2 phenotype. Serologic investigations were performed on patients' red blood cells and serum. The KEL gene analysis was done by using a BeadChip assay (HEA Version, 1.2, Immucor), real-time polymerase chain reaction, and/or sequencing of all 19 exons of the KEL gene.
  
  
  RESULTS
  In KEL:-5 patients, two novel KELnull alleles were described: 821G>A being the second described KELnull allele on a KEL*01 backbone and 184Tdel. In the 121 KEL:1,-2 individuals, nine (7.4%) were found to display a discordant KEL:1,-2 phenotype and KEL*01/KEL*02 genotype. Three novel silent KEL*02 alleles were described: 1084C>A, 1708G>A, and IVS11+5g>a.
  
  
  CONCLUSIONS
  The number of silent KEL alleles and the notion that KEL null alleles are on a KEL*02 background may evolve in the coming years. Systematic DNA analysis showed that the number of discordant phenotype/genotype results, related to silent KEL*02 alleles was higher than expected in France. These data emphasize that clinical practice based on DNA analysis for blood group antigens requires caution and should improve the performance of the blood group phenotype prediction.
authors.affiliation: Institut National de la Transfusion Sanguine, CNRGS-INSERM U665, Paris; CHU Réunion, Site Sud, Saint Pierre, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Martin-Blanc
authors.forename: Philippe
authors.initials: P
authors.lastname: Simon
authors.forename: Dominique
authors.initials: D
authors.lastname: Gien
authors.forename: Sandrine
authors.initials: S
authors.lastname: Kappler-Gratias
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Le Pennec
authors.forename: Bach-Nga
authors.initials: BN
authors.lastname: Pham
mesh_terms: D000483:Alleles; D001788:Blood Grouping and Crossmatching; D001803:Blood Transfusion; D005260:Female; D005602:France; D020868:Gene Silencing; D005838:Genotype; D006801:Humans; D007626:Kell Blood-Group System / Q000235:genetics* / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D008666:Metalloendopeptidases / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D011247:Pregnancy; D012698:Serologic Tests
chemical_list: D007626:Kell Blood-Group System; D008562:Membrane Glycoproteins; C585978:KEL protein, human; D008666:Metalloendopeptidases