RESUMO
BACKGROUND: The clinically important Kidd (JK) blood group system is considered to be relatively uncomplicated, both serologically and genetically. The JK*01 and JK*02 alleles give rise to Jk(a) and Jk(b) antigens, respectively, and silenced alleles result in Jk(a-b-). Other inherited variants analogous to Fy(x) and weak D phenotypes have not been characterized for JK, although recent abstracts indicate their presence. STUDY DESIGN AND METHODS: Six index samples from individuals whose RBCs reacted variably or weakly with different sources of anti-Jk(a) and 300 controls of the four known JK phenotypes were investigated by standard serology, flow cytometry, Western blotting, and the urea hemolysis test. Molecular analysis, including allele-specific polymerase chain reaction (PCR), DNA sequencing, and transcript analysis by real-time PCR, was performed. RESULTS: All Jk(a+(w)b-) and Jk(a+(w)b+) index samples were homo- or heterozygous for an altered JK*01 allele carrying 130G>A (Glu44Lys) and the JK*02-associated silent SNPs 588G and Intron 9 -46g. Blood donor screening indicated an allele frequency of 0.042. Titration and flow cytometry with anti-Jk(a) gave lower values in index samples compared to controls, as did anti-Jk3 titers. Donors with 130A also showed significantly decreased Jk(a) density by flow cytometry versus 130G. Western blotting with anti-UT-B demonstrated weaker reactivity with Jk(a+(w)) membranes while JK mRNA levels could not discriminate index samples from controls. The urea hemolysis test was only moderately affected in two Jk(a+(w)b-) samples. CONCLUSIONS: A new phenotype with weakened Jk(a) expression on RBCs is associated with a JK*01-like allele, which may constitute a risk for hemolytic transfusion reactions if antigen-positive units are missed by routine serology.
Assuntos
Tipagem e Reações Cruzadas Sanguíneas , Sistema do Grupo Sanguíneo Kidd/genética , Proteínas de Membrana Transportadoras/genética , Alelos , Substituição de Aminoácidos , Anticorpos Anti-Idiotípicos/imunologia , Western Blotting , Feminino , Citometria de Fluxo , Regulação da Expressão Gênica , Hemólise , Humanos , Masculino , Proteínas de Membrana Transportadoras/biossíntese , Proteínas de Membrana Transportadoras/imunologia , Fenótipo , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Análise de Sequência de DNA , Transcrição Gênica , Transportadores de UreiaRESUMO
BACKGROUND: The Kidd blood group antigens Jka and Jkb are encoded by the red blood cell (RBC) urea transporter gene. Homozygosity for silent JK alleles results in the rare Jk(a-b-) phenotype. To date, seven JKnull alleles have been identified, and of these, two are more frequent in the Polynesians and Finns. This study reports the identification of other JKnull alleles in Jk(a-b-) individuals of different ethnic or geographic origins. STUDY DESIGN AND METHODS: Nine Jk(a-b-) samples and a sample from a Jk(a-b+) mother of a Jk(a+b-) baby were investigated. Polymerase chain reaction amplification and sequence analysis of the JK gene was performed. Western blotting and urea lysis were used to confirm Jk(a-b-) RBCs. RESULTS: Four novel alleles were identified: two different nonsense mutations, 202C>T (Gln68Stop) and 723delA (Ile262Stop) were identified on otherwise consensus JK*1 and JK*2 alleles, respectively. A missense mutation, 956C>T (Thr319Met), was identified in a JK*1 allele from an African-American and a JK*2 allele in two people of subcontinental Indian descent. Immunoblotting and urea lysis confirmed absence of JK glycoprotein in RBC membranes from a sample carrying the 956C>T mutation. Other previously described JKnull mutations were found in samples of origins other than in which they were first identified. CONCLUSION: The molecular bases of the Jk(a-b-) phenotype are diverse and this is the first report of JKnull alleles in individuals of African and subcontinental Indian descent. Although rare, these alleles should be taken into consideration when planning genotyping strategies for blood donors and patients.
Assuntos
Alelos , Células Eritroides/metabolismo , Sistema do Grupo Sanguíneo Kidd/genética , Proteínas de Membrana Transportadoras/deficiência , Sequência de Bases , Genoma Humano/genética , Humanos , Íntrons/genética , Sistema do Grupo Sanguíneo Kidd/análise , Sistema do Grupo Sanguíneo Kidd/química , Mutação/genética , Transportadores de UreiaRESUMO
BACKGROUND: The absence of all Kell blood group antigens (K(0) phenotype) is very rare. K(0) persons, however, can produce clinically significant anti-Ku (K5) after transfusion and/or pregnancy and require K(0) blood for transfusion. Ten alleles giving rise to the K(0) phenotype have been reported: different populations were studied although none from Scandinavia. STUDY DESIGN AND METHODS: Three K(0) samples were identified by blood banks in Sweden (Uppsala, Umeå, and Linköping) during a 20-year period. Kell antigen typing was performed with standard serologic techniques by the respective blood banks and K(0) status was confirmed by the International Blood Group Reference Laboratory in Bristol, England. Polymerase chain reaction and DNA sequencing of the KEL coding region (exons 1-19) was performed on genomic DNA. RESULTS: The Uppsala K(0) was homozygous for a 1540C>T substitution in exon 13, leading to an immediate stop codon. The Umeå K(0) was homozygous for 1023delG in exon 8 that results in a frameshift and a premature stop codon in exon 9. In the Linköping K(0), a previously reported mutation g>a at +1 of intron 3 was found. CONCLUSION: Two novel and one previously reported null alleles at the KEL locus are described. The identified nonsense mutations abolish expression of the Kell glycoprotein and are thus responsible for the K(0) phenotype in these Swedish families.