title: A McLeod phenotype detected by random screening for K:-4 [Kp(b-)] blood donors in Brazil.
abstract: BACKGROUND
  The red blood cells of the McLeod phenotype have weak expression of Kell System antigens due to no expression of XK protein.
  
  
  METHODS
  One blood donor reacted as K:-4 [Kp(b-)] during a screening assay. Subsequent serologic studies demonstrated weak expression of K:4 and all other high-incidence Kell system antigens tested; however, no expression of Kx antigen was observed.
  
  
  RESULTS
  One apparently healthy blood donor demonstrated low expression of K:2, K:4, K:5, K:7, K:14, K:22, and no Kx antigen in his red blood cells. His brother and mother showed the same weak expression, and his father showed normal expression of antigens tested. Flow cytometry studies confirmed the mother's status as a McLeod carrier female. Genotyping determined the presence of KEL2 and KEL4 alleles in mother and siblings. Southern blot with an exon-1 probe showed fragments shorter than predicted for the siblings and the mother, suggesting a deletion. Polymerase chain reaction with primers spanning exon 1 and flanking regions displayed a similar pattern. Deoxyribonucleic acid sequence allowed the precise characterization of a deletion of 392 bp, beginning at the 5' of the coding region up to nucleotide 201 of exon 1, which putatively abrogates the production of XK protein.
  
  
  CONCLUSIONS
  Two brothers with McLeod phenotype in a Brazilian blood-donor population were identified. The molecular basis for this phenotype is a 392-bp deletion spanning from 5' of the coding region to exon 1 of the XK gene, never described before.
authors.affiliation: Hospital Sírio Libanês Blood Bank, the Centro de Imunologia e Imunogenética, Hospital das Clínicas da Faculdade de Medicina da USP, São Paulo, Brazil. snwendel@uninet.com.br
authors.forename: Silvano
authors.initials: S
authors.lastname: Wendel
authors.forename: Rita
authors.initials: R
authors.lastname: Fontão-Wendel
authors.forename: José Eduardo
authors.initials: JE
authors.lastname: Levi
authors.forename: Maria Giselda
authors.initials: MG
authors.lastname: Aravechia
authors.forename: Roberta F S
authors.initials: RF
authors.lastname: Bordokan
authors.forename: David
authors.initials: D
authors.lastname: Russo
authors.forename: Monica Santoro
authors.initials: MS
authors.lastname: Haddad
mesh_terms: D000328:Adult; D026921:Amino Acid Transport Systems, Neutral / Q000172:deficiency* / Q000235:genetics; D000942:Antigens, Bacterial / Q000097:blood*; D000954:Antigens, Surface / Q000097:blood*; D001483:Base Sequence; D001782:Blood Donors; D015153:Blotting, Western; D001938:Brazil; D004247:DNA / Q000097:blood; D004912:Erythrocytes / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D017353:Gene Deletion; D005838:Genotype; D006801:Humans; D007626:Kell Blood-Group System / Q000097:blood* / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D000942:Antigens, Bacterial; D000954:Antigens, Surface; C030659:K antigens; D007626:Kell Blood-Group System; C087883:XK protein, human; D004247:DNA