Serologic Variability of the A(var) (784G>A) and Its Property of Different Expression Depending on Co-inherited ABO Allele / 대한수혈학회지

BACKGROUND: A allele, A(var), characterized by a 784G>A polymorphism (Asp262Asn) has been identified only in Korean A(weak)B donors. This study evaluated the serological and genetic characteristics of thirteen samples with newly identified A(var) allele. METHODS: This study examined 10 samples with the A(var) allele including 4 members from a family, who were randomly obtained from blood donors recruited at Gwangju-Chonnam Red Cross Blood Center, and patients at the Chonnam National University Hospital. Routine ABO serologic tests, ABO genotyping using an allele specific polymerase chain reaction (AS-PCR), and the sequencing of exon 6 and 7 of ABO gene were performed on all samples. In addition, sequencing of exon 1~5 of the ABO gene was carried out on two randomly selected samples. RESULTS: The A(var) allele was identified in nine A(weak)B and one O (II-1 of the family study) sample. Eight of these nine individuals showed 1+ agglutination with the monoclonal anti-A reagents on forward typing but one sample showed no agglutination. Weak anti-A was detected in all sera. From the family study, the A(var) allele, which was transmitted from the propositus through her descendant (II-1, II-3 and III-1), produced either the weak A phenotype when inherited with a B allele or the O phenotype when inherited with an O allele. CONCLUSION: A(var) erythrocytes showed different agglutination patterns to anti-A. Different expressions (possible allelic enhancement) were observed depending on the co-inherited ABO alleles from samples with the A(var) allele.

A Family Study of Ael02 Allele Expressing Different Phenotypes Depending on Co-inherited ABO Alleles / 대한수혈학회지

Compared with A101, Ael02 is characterized by 467C>T, 646T>A and 681G>A polymorphisms, resulting in two amino acid substitutions (Pro156Leu and Phe216Ile). The first study in Korea was reported at 2003. However, only unrelated donors were characterized. This study carried out molecular genetic analysis of a 26 year-old male propositus diagnosed with the Ael subgroup by serological tests along with his family. The propositus had the genotype Ael02/B101 expressing the AelB phenotype, and his father the genotype Ael02/O01 expressing the O phenotype. These findings suggest that the AelO2 allele is expressed as different phenotypes depending on the co-inherited ABO alleles.

Resolution of ABO Discrepancies by ABO Genotyping / 대한진단검사의학회지

BACKGROUND: Before a blood transfusion, both red cell and serum typing need to be matched for ABO tests on the donor and patient (recipient). When a mismatch exists in the tests, additional ABO genotyping and serological tests are required for the resolution of the discrepancy. We performed ABO genotyping on a series of blood donors and patients with ABO discrepancies to assist in resolving their blood groups. METHODS: We examined 46 samples with ABO discrepancies from a random pool of donors recruited at Gwangju-Chonnam Red Cross Blood Center and from patients at Chonnam National University Hospital between May 2004 and July 2005. ABO genotyping was performed on all samples with an allele specific polymerase chain reaction for differentiation of A, B,O, cis-AB, A(var) (784 G>A), and B(var) (547 G>A) alleles; routine serologic tests were also performed. Exon 6 and 7 of ABO gene from five samples were sequenced. RESULTS: The genotypes of 18 donors/patients with weakened A or B antigen expressions consisted of 4 cases of cis-AB/O (3 A(2)B(3), 1 A(2)B); 5 cases of cis-AB/A (5 A(1)B(x or el)); 2 cases of A/O (1 O, 1 A(m or x)); 1 case of B/O (1 B(m or x)); 4 cases of A/B (1 A(2)B , 1 A(1)B(x or el), 2 A(1)B(3)); and 2 cases of A(var)/B (2 A(w)B). On the other hand, the genotypes of 28 samples with unexpected serum reactions included 18 cases of A/O (16 A(1), 2 A(int)); 7 cases of A/A (5 A(1), 1 A(1)B(x or el), 1 A(1)B(w)); and 3 cases of O/O (1 O, 2 B(w)). CONCLUSIONS: ABO genotyping is useful for differentiating the ABO discrepancies that were difficult to resolve by serological tests. The most frequent unusual red cell reactions were weak A and B antigen expressions, which were resulted from the ABO subgroup alleles including cis-AB allele, whereas the most frequent unusual serum reactions were caused by decreased anti-B titers.

A Simplified ABO Genotyping by Allele-Specific Polymerase Chain Reaction / 대한진단검사의학회지

BACKGROUND: Genotyping of ABO gene could be more informative and valuable than serological typing in some situations such as the resolution for ABO discrepancy between the cell typing and serum typing and determination of A and B subgroups. We developed a simple allele-specific polymerase chain reaction (AS-PCR) method without the use of any restriction enzymes to detect the A, B, O, and cis-AB alleles for Koreans. METHODS: An AS-PCR was designed with amplification refractory mutation system (ARMS) at nt (nucleotide) 261 (exon 6) and at nt 526, 803 (exon 7) of ABO gene to detect specific nucleotide sequence differences between the ABO alleles. We tested for ABO genotyping 60 DNA samples previously tested by PCR-RFLP and stored at -70degreeC. These samples had been obtained from blood donors recruited at the Gwangju-Chonnam Red Cross Blood Center between July 2002 and February 2003. RESULTS: With our new PCR method, the genotypes of the 60 samples were found to be A/O (n=10), A/A (n=5), B/O (n=10), B/B (n=5), O/O (n=10), cis-AB/A (n=5), cis-AB/B (n=5), and cis-AB/ O (n=10), which were the s ame results obtained previously with PCR-RFLP. CONCLUSIONS: Our AS-PCR is a simple and accurate method for the detection of A, B, O, and cis-AB alleles for Koreans.