ABO Antigen Expression Research Articles

Prevalence and distribution of serological characteristics of weak ABO subgroups in the Chinese population

ObjectivesThis study aimed to determine the true frequency of weak ABO subgroups and to investigate the serological characteristics of various subgroup alleles in the Chinese population. MethodsA total of 2,945,643 blood samples were collected from January 2009 to December 2017. After initial screening and re-examination using automatic blood group analyzers, all ABO-discrepant samples were confirmed by standard serological analysis and molecular detection by DNA sequencing. The true frequency of weak ABO subgroups was determined by the number of ABO subgroup donors and the missed detection rate. The ABO antigen expressions corresponding to subgroup alleles were analyzed by the agglutination intensity of red blood cells. ResultsThe detection rate of ABO subgroups was 0.031 % (927/2,945,643). Considering the missed detection rate (27.81 %), the true frequency of ABO subgroups in the Chinese population was 0.044 %. The three most common genetic variations among blood donors in Shanghai were BA.04, BW.12 and BA.02. BW.03 showed the weakest B antigen expression (6.00 ± 1.97) and Bvar-1 the strongest (9.20 ± 1.10). ConclusionMany ABO subgroups were missed. BA.04 was found to be the most common subgroup allele in the Chinese population. Different ABO subgroup alleles exhibit different ABO antigen expression patterns.

Exploring the diverse biological significance and roles of fucosylated oligosaccharides.

Long since, carbohydrates were thought to be used just as an energy source and structural material. However, in recent years, with the emergence of the field of glycobiology and advances in glycomics, much has been learned about the biological role of oligosaccharides, a carbohydrate polymer containing a small number of monosaccharides, in cell-cell interaction, signal transduction, immune response, pathogen adhesion processes, early embryogenesis, and apoptosis. The function of oligosaccharides in these processes is diversified by fucosylation, also known as modification of oligosaccharides. Fucosylation has allowed the identification of more than 100 different oligosaccharide structures that provide functional diversity. ABO blood group and Lewis antigens are among the best known fucosyl-linked oligosaccharides. In addition, the antigens in the ABO system are composed of various sugar molecules, including fucosylated oligosaccharides, and Lewis antigens are structurally similar to ABO antigens but differ in the linkage of sugars. Variation in blood group antigen expression affects the host's susceptibility to many infections. However, altered expression of ABO and Lewis antigens is related with prognosis in carcinoma types. In addition, many pathogens recognize and bind to human tissues using a protein receptor with high affinity for the fucose molecule in glycoconjugates, such as lectin. Fucosylated oligosaccharides also play vital roles during fertilization and early embryogenesis. Learning and memory-related processes such as neurite growth, neurite migration, and synapse formation seen during the development of the brain, which is among the first organs to develop in embryogenesis, are regulated by fucosylated oligosaccharides. In conclusion, this review mentions the vital roles of fucosylated oligosaccharides in biology, drawing attention to their importance in the development of chemical tools to be used in function analysis and the investigation of various therapeutic targets.

Association of Secretor And Nonsecretor Status with Lewis Phenotyping Among Blood Donors: A Prospective Observational Study from Tertiary Care Hospital.

ABO (ABH) antigen expression on red cell antigens and secretion of ABH substances in body fluids are governed by different genes. The presence or absence of the Secretor gene is the basis of secretor status positivity and negativity, respectively. Determination of the secretor status has an essential role in the medical field. It was a prospective observational study to determine the association of secretor and nonsecretor status with Lewis phenotyping among voluntary blood donors. It was conducted from Jan 2020 to December 2021 at the Department of Transfusion Medicine in a tertiary care hospital in South India. Among 318 donors, secretors were 229 (72%), and nonsecretors were 89 (28%). The Lewis phenotype was consistent with secretor status, i.e., All Le (a-b +) were secretors accounting for 213 (66.9%), and All Le(a + b-) were nonsecretors accounting for 80(25.1%)donors. In the Le(a-b-) phenotype, 16(5.0%) were secretors with Se positivity but defective Lewis expression, and 9(2.8%) were nonsecretors with sese. Detection of Lewis phenotype indirectly reflects the blood group secretor status. Hence, in case of discrepancies in ABO blood groups, Bombay and Para Bombay groups, testing for Le(b) confirmation will be useful.

ABO and Rh Blood Group Antigens and Natural Anti-A and ANTI-B Antibodies in the Neonates

ABO blood group is determined by the presence or absence of A and B antigens on the surface of RBC and of anti-A and anti-B antibodies in the serum. The relatively weak expression of A and B antigens in newborns due to their developing immune systems poses challenges in accurately detecting naturally occurring IgM antibodies against these antigens. This difficulty in immunoserological methods contributes to the potential for errors in determining the blood groups of newborns. Despite this, the Rh antigen expression in newborns remains comparable to that in adults. Nonetheless, various factors contribute to diverse blood typing results in newborns, including the utilization of alternative testing methods. The complexity of blood typing is magnified when using samples from the umbilical vein. Furthermore, compared to adults, the exploration of ABO antigen expression in newborns is limited, and the identification of specific subgroups such as A1 and A2 is even rarer. This underscores the need for standardized testing procedures and further research to enhance our understanding of antigen expression patterns in newborns. Based on the aforementioned details, the primary objective of our study was to delve into specific aspects related to blood group characterization in newborns. This encompassed exploring the expression of A, B, AB, and D antigens on the surface of red blood cells (RBCs) and detecting anti-A and anti-B antibodies in the plasma of newborns. These analyses were conducted using samples obtained from the heels of 208 newborns and were typed by forward and reverse blood typing methods with monoclonal antibodies and srandart erythrocytes. The distribution of phenotypic groups within the ABO system among the newborns was not uniform. The r allele was identified with the highest frequency in the analyzed samples (0.6), while the prevalence of the p allele significantly lags at 0.3. The q allele has the lowest frequency (0.1). In our study, we propose that for the majority of cases (43.94±3.5%) among the studied newborns, there was an absence of naturally occurring anti-A and anti-B antibodies (n=87). In a specific scenario, within the O(I) blood group nwborns, partial synthesis of these antibodies was detected in 14.14±2.4% (n=28). Meanwhile, 41.92±3.5% of the newborns in our study exhibited natural antibodies similar to those found in adults. We didn’t find any difficulties in typing the Rh blood group antigens in the newborns. In conclusion, our study's findings indicate that newborns, in certain instances, exhibit strongly pronounced natural anti-A and anti-B antibodies within the ABO system. However, in the majority of cases, these antibodies are not evident. Majority of cases erythrocyte A and B antigens were weakly expressed and for detecting these images optic microscopes were used.

The fate of donor-type ABO blood group antigen expression in liver grafts in ABO-incompatible adult living donor liver transplantation.

Donor-type ABO blood group antigens (dABOAgs) have been detected in ABO-incompatible adult living donor liver transplantation (ABOi ALDLT) grafts, but their fate and role in ABOi ALDLT rejection remain uncertain. The 0-day, <1-month, and 1-year serial liver graft biopsies from 30 ABOi ALDLT recipients were retrospectively evaluated. ABO antigen expression was quantitatively and serially measured by the mean number of positively stained vascular structures (endothelium of the capillaries, arteries, hepatic veins, and portal veins) within the portal tracts (sS). The dABOAg sS counts of 0-day, <1-month, and 1-year liver graft biopsies (32.3, 20.8, and 20.6, respectively) decreased significantly (p < .001). Early rejection in the <1-month biopsy was observed in 8/30 (26.7%) recipients, four (13.3%) of whom showed antibody-mediated rejection. The sS counts tended to rebound in grafts showing early rejection, with minimal changes from the 0-day to <1-month period, but increased to pre-transplantation levels after 1year, compared to that in grafts without early rejection (36.0, 20.4, 19.6 vs. 23.7, 21.9, 23.0, respectively; p=.040). While dABOAg expression decreased after ABOi ALDLT, recipients showing early rejection showed sustained graft dABOAg expression. Therefore, dABOAg expression may be involved in the mechanism of accommodation in ABOi transplantation.

Association between diminished miRNA expression and the disease status of AML patients: Comparing to healthy control

BackgroundChanges in ABO blood type caused by a gradual decrease in antigen expression have been found in patients with acute myeloid leukemia (AML). Studies have indicated that alteration of ABO gene methylation accounts for 50% of acquired weak ABO antigen expression in patients with leukemia. However, the molecular mechanisms contributing to the remaining 50% of cases are unknown. We hypothesize that deregulation of miRNA is correlated with weak ABO antigen expression in patients with AML. MethodsBlood samples of 19 patients with AML and 12 healthy controls were collected, in which the blood type was not changed in these AML patients. Flow cytometric analysis was applied to measure the ABO antigen expression titer among AML patients and controls. A total of 18 leukemia-related miRNAs were analyzed via quantitative real-time polymerase chain reactions. ResultsWe found that miRNA profiles were correlated with the AML patients, especially in those who had constant or weakened ABO antigen expressions. Compared with healthy controls, the miR-16 and miR-451 expression were significantly lower in either AML cases with weak ABO antigen expressions (p = 0.003, p = 0.028, respectively) or AML cases with constant ABO antigen expressions (p = 0.043, p = 0.040, respectively). Although not statistically significant, decreasing trends in the miR-451 and miR-16 expressions in the AML patients with weakened ABO were observed compared to those with constant ABO antigens. The weak ABO antigen expression might correlate with miRNAs, especially miR-16 and miR-451. ConclusionThis study indicated that decreasing in miR-16 and miR-451 was associated with AML and AML with weakened ABO expression. In the future, we will continue to include more cases and exclude the others factor influencing ABO antigen expression, promoter methylation and oxidative stress, to replicate the results of this study and investigate the underlying mechanism of decreasing miR-16 and miR-451 in AML patients with varied ABO antigen expression levels.

Resolving blood group discrepancy in a patient with acute myeloid leukemia: A case report

Introduction. The ABO blood group antigens are determined by genes located at three separate genetic loci. Loss or weakening of ABO antigens is often associated with hematological malignant diseases, but also solid tumors in the body. A change in the expression of ABO antigens leads to discrepancies when determining the patient?s blood group and carries the risk of incompatible transfusions. Case Report. During the blood typing of a 27-year-old female patient with a diagnosis of acute myeloid leukemia, there were discrepancies in the interpretation of the ABO blood group. Since the confirmation blood group indicated that it was blood group O, when determining the reverse blood group, the reading showed the absence of the expected agglutination of group A1 and B red blood cells. By examination of the patient?s records, as well as confirmation genotyping, the blood group A was established. After the patient entered the remission phase of the disease, the A Rhesus D positive blood group was determined, without discrepancies during testing. Conclusion. Changes in blood groups can occur even before the diagnosis of hematological malignant disease is established. For this reason, it is extremely important to thoroughly examine any discrepancy during blood typing in order to provide patients with safe blood.

Survey and characterization of nonfunctional alleles of FUT2 in a database

The expression of ABO antigens in human saliva is regulated by the FUT2 gene, which encodes a secretor type α(1,2)fucosyltransferase. Secretors express ABO substrates in saliva and non-secretors do not. Secretor status is an object of concern, especially for susceptibility to various infectious diseases. A multitude of single nucleotide polymorphisms (SNPs) and copy number variations (CNVs) have been reported, and they show unique distributions among different populations. In this study, we selected 18 uncharacterized FUT2 alleles listed in the Erythrogene database and obtained genomic DNA having these alleles. We experimentally confirmed the haplotypes, but 10 of 18 alleles disagreed with those in the database, which may be attributed to their low frequency. We then examined the activity of the encoded α(1,2)fucosyltransferase for 13 alleles by flow cytometry of H antigen expression. The impact of each nonsynonymous SNP on the enzyme was also estimated by software. We finally identified two non-secretor alleles (se610and se357,856,863) and one weak secretor allele (se262,357), while in silico analysis predicted that many alleles impair the function. The present results suggest that correct haplotyping and functional assays are desirable for analysis of the FUT2 gene.

New ABO intron 1 variant alleles.

Abstract Unusual and discrepant ABO phenotypes are often due to genetic variants that lead to altered levels or activity of ABO transferases and consequently to altered expression of ABO antigens. This report describes eight genetic alterations found in 15 cases with reduced or undetectable expression of ABO antigens. Forward and reverse ABO grouping was performed by standard gel or tube methods. Adsorption-heat elution and saliva testing for H and A substances followed the AABB technical manual procedures. Genomic DNA extracted from whole blood was PCR-amplified to cover the entire ABO coding sequence, splice junctions, proximal promoter, and intron 1 enhancer. Amplification products were sequenced by next-generation or Sanger dideoxy methods, either directly or after cloning into a bacterial plasmid vector. Eight unreported alleles were found in the 15 cases analyzed. Alleles ABO*A(28+1C) and ABO*A(29–5G) harbor variants that alter the consensus sequence at the intron 1 donor and acceptor splice sites, respectively. The other alleles harbor variants that alter the consensus sequence at transcription factor–binding sites in the intron 1 enhancer: specifically, ABO*A(28+5792T), ABO*A(28+5859A), and ABO*A(28+5860G) at GATA-1 sites; ABO*B(28+5877T) and ABO*B(28+5878G) at a RUNX1 site; and ABO*A(28+5843A) at or near a C/EBP site. Molecular and serologic characterization of ABO alleles can help in their future identification and in the resolution of discrepancies.

Histo-Blood Group Antigens in Oral Cancer and Potentially Malignant Disorders.

Background:Early detection of oral cancer is of critical importance because survival rates markedly improve when oral lesions are identified at an early stage. Aim of the present study is to investigate the expression of ABO (H) antigens in tissue specimens of oral cancer and potentially malignant disorders and to determine the role of ABO (H) antigens in tumour staging. Materials and Methods:A prospective study was conducted on 60 cases of oral cancer and potentially malignant diseases. Specific red cell adherence test (SRCA-test) was used for studying A, B and O (H) antigens in tissue specimens and iso-antigenicity of epithelium was graded according to degree of adherence of indicator red blood cells. Results:Among OSMF group, grade II adherence was seen in 53.3% cases, grade III in 33.3% cases, grade IV in 13.3% cases. In leukoplakia group, grade II adherence was seen in 26.7% cases, grade III adherence in 53.3% cases, grade IV adherence in 20% cases. Within the leukoplakia group, cases with dysplasia showed decreased adherence, compared with cases without dysplasia. Oral cancer group, negative adherence was seen in 13.3% cases, grade I adherence in 46.7% cases, grade II in 40% cases. In oral cancer group, antigen reactivity was less in poorly and moderately differentiated carcinoma, compared to well differentiated carcinoma. Conclusions:Antigen adherence and degree of loss of ABO (H) antigens in tissue specimens can be used for staging of the tumour.

Molecular Basis of ABO Variants Including Identification of 16 Novel ABO Subgroup Alleles in Chinese Han Population

Introduction: The characteristic of ABO blood subgroup is crucial for elucidating the mechanisms of such variant phenotypes and offering useful information in blood transfusion. Methods: In total, 211 ABO variants including part of available family members were investigated in this study. The phenotypes of these individuals were typed with serologic methods. The full coding regions of ABO gene and the erythroid cell-specific regulatory elements in intron 1 of them were amplified with polymerase chain reaction and then directly sequenced. The novel alleles were confirmed by cloning and sequencing. Phylogenetic tree was made using CLUSTAL W software. 3D structural analyses of the glycosyltransferases (GTs) with some typical mutations were performed by PyMOL software. Results: Forty-eight distinctly rare ABO alleles were identified in 211 Chinese variant individuals, including 16 novel ABO alleles. All of the alleles were categorized as 5 groups: 16 ABO*A alleles, 23 ABO*B alleles, 4 ABO*BA alleles, 4 ABO*cisAB alleles, and 1 ABO*O alleles. ABO*A2.08 and ABO*BA.02 were the relatively predominant A and B subgroup alleles, respectively. According to the phylogenetic tree, 28 alleles (5 common alleles and 23 alleles identified in our laboratory) were classified into 3 major allelic lineages. The structural analysis of 3D homology modeling predicted reduced protein stability of the mutant GTs and may explain the reduced ABO antigen expression. Conclusions: The molecular basis of ABO variants was analyzed, and 16 novel ABO alleles were identified. The results extended the information of ABO variants and provided a basis for better transfusion strategies and helped to improve blood transfusion safety.

Std fimbriae-fucose interaction increases Salmonella-induced intestinal inflammation and prolongs colonization.

Expression of ABO and Lewis histo-blood group antigens by the gastrointestinal epithelium is governed by an α-1,2-fucosyltransferase enzyme encoded by the Fut2 gene. Alterations in mucin glycosylation have been associated with susceptibility to various bacterial and viral infections. Salmonella enterica serovar Typhimurium is a food-borne pathogen and a major cause of gastroenteritis. In order to determine the role of Fut2-dependent glycans in Salmonella-triggered intestinal inflammation, Fut2+/+ and Fut2-/- mice were orally infected with S. Typhimurium and bacterial colonization and intestinal inflammation were analyzed. Bacterial load in the intestine of Fut2-/- mice was significantly lower compared to Fut2+/+ mice. Analysis of histopathological changes revealed significantly lower levels of intestinal inflammation in Fut2-/- mice compared to Fut2+/+ mice and measurement of lipocalin-2 level in feces corroborated histopathological findings. Salmonella express fimbriae that assist in adherence of bacteria to host cells thereby facilitating their invasion. The std fimbrial operon of S. Typhimurium encodes the π-class Std fimbriae which bind terminal α(1,2)-fucose residues. An isogenic mutant of S. Typhimurium lacking Std fimbriae colonized Fut2+/+ and Fut2-/- mice to similar levels and resulted in similar intestinal inflammation. In vitro adhesion assays revealed that bacteria possessing Std fimbriae adhered significantly more to fucosylated cell lines or primary epithelial cells in comparison to cells lacking α(1,2)-fucose. Overall, these results indicate that Salmonella-triggered intestinal inflammation and colonization are dependent on Std-fucose interaction.

ABO antigen levels on platelets of normal and variant ABO blood group individuals

Although differential expression of ABO antigens on platelets is related to recipients’ platelet recovery and neonatal alloimmune thrombocytopenia in ABO-incompatible transfusion and pregnancy, the expression of ABO antigens on platelets in normal and variant ABO blood group individuals is rarely reported. Here, we analyzed the expression of ABO antigens on platelets in a cohort of 515 individuals with normal and variant ABO. The variants were also genotyped for ABO and/or FUT1 loci to distinguish inherited or acquired ABO variants. The results showed that ABO antigens expression on individual platelets was relatively stable during the storage period in vitro. The frequency of low-, moderate-, and high-expression phenotype in normal individual was 59.6%, 35.5%, and 4.9%, respectively. The platelets from para-Bombay and most inherited ABO subgroups express very low levels of ABO antigens, but the acquired ABO variants and the B3 subgroup express normal or abnormally high levels of ABO antigens on platelets. The data extend the information of antigens expression on platelets, which may help to improve the strategy of platelets transfusion.

A novel mutation +5904 C>T of RUNX1 site in the erythroid cell-specific regulatory element decreases the ABO antigen expression in Chinese population.

An erythroid cell-specific regulatory element (+5·8-kb) in the first intron of ABO is responsible for the antigen differential expression and the regulatory activity of the element was affected by the nucleotide mutation in the +5·8-kb region. Currently, many individuals with ABO subgroups were found in the Chinese population, but there was little information about the function of +5·8-kb region in these individuals. Here, we studied the mechanism of the mutation in the +5·8-kb region responsible for reducing of antigen expression in 30 ABO subtype Chinese individuals without mutation in the coding region or splicing site. The nucleotide sequence of the partial intron 1 covering the +5·8-kb site was amplified and directly sequenced. The haplotype with the novel mutation was obtained by the TOPO TA cloning. Both of the ABO promoter and the +5·8 kb regulatory element were subcloned into the basic luciferase reporter plasmid using the double endonuclease digestion. The promoter activity was examined by the dual-luciferase report vector with K562 cells. A novel nucleotide substitution +5904 C>T located at RUNX1-binding site in the +5·8 kb site was identified from three individuals with B subtypes. +5890 T>G were found in three Bel and one Ael phenotypes. Cotransfection and luciferase assays demonstrated that the +5904 C>T could obviously reduce activity of the +5·8 kb site. The study suggested that the transcriptional activity of the +5·8 kb site could be downregulated by the single point mutation of RUNX1 motif, leading to reduction in A or B antigen expression.

False-Positive Flow-Cytometric T Cell Crossmatch caused by Blood Type Antigen Expressed on Lymphocytes in ABO Incompatible Kidney Transplantation

Background Flow-cytometric T cell crossmatch (FTXM) uses live donor lymphocytes to detect anti-donor-human leukocyte antigen (HLA) IgG antibodies. Therefore, the results can be affected by individual cell surface molecular expression. Herein we report three cases with FTXM false-positive living-related kidney transplants whose positivity was influenced by the expression of incompatible ABO blood-type antigens. Patients and Methods The kidney recipients were three men with blood type O who received from their wives with blood type B. Their anti-B IgG titers were 1:32, 1:128, and 1:256. Lymphocyte cytotoxic assays were negative in all cases. Median of mean channel shift (MCS) in FTXM was 78.7% (range, 52.8%–85.7%). There were no anti-HLA (either donor-specific or not) class I IgG antibodies in all 3 cases detected by a solid-phase bead assay. We hypothesized that non-HLA antigens expressed on T lymphocytes affect false-positive FTXM results. To examine this, we incubated the patients’ sera with donor-type red blood cells (RBCs) to adsorb anti-ABO antibodies prior to FTXM. Results When the incubated sera were tested in FTXM with donor T lymphocytes, the results were negative in all cases with median MCS 3.75% (0.0%–7.5%). To clarify the expression of ABO antigens on the donor T lymphocytes, we incubated donor T lymphocytes with recipients’ sera and then incubated the cells with acid solution to detach the bound antibodies from the T lymphocytes. The eluates showed agglutination in indirect Coombs test with blood type B RBCs but no agglutination with O blood type RBCs. This indicates that the donor T lymphocytes expressed blood type B antigen and anti-blood type IgG antibodies reacted with the B antigen. These results show that anti-blood type IgG antibodies can bind to ABO-blood type antigens on the surface of T lymphocytes, resulting in positive FTXM. The false-positive FTXM can be excluded by short-term incubation of recipients’ sera with donor-type RBCs. Conclusion In ABO-incompatible kidney transplantation, anti-blood type IgG antibodies can be detected as anti-donor IgG antibodies in FTXM.

The relationship between immunogenic red blood cell antigens and Human Immunodeficiency Virus infection

IntroductionEvidence suggests that red cell antigens may act as receptors for viruses and bacteria and therefore could be associated with HIV infection. Previous studies have been controversial and therefore the aim of this exploratory study was to analyse the expression of immunogenic red cell antigens in HIV-seropositive individuals and to compare the results to negative donors from South Africa. MethodsThe expression of ABO, Rh, Kell and Duffy antigens from 119 HIV-seropositive patients was compared to 317 HIV-seronegative blood donors. Nucleic acid amplification testing and PCR were used to determine the HIV status and the ID-Gel Card Technology was used to determine the blood group antigen profile. ResultsThere was no significant difference in the expression of A, B, AB, Duffy or Kel antigens between the two groups but significantly lower numbers of HIV+ individuals were O Rh Negative (p = ,0.0001). Analysis of those with a Duffy null phenotype revealed a significantly higher incidence of blood type A RH1-Positive, Dce/R0r and B RH1-Positive, DcEe/R2r within the HIV-seropositive group (p = < 0.05). None of the HIV-seropositive individuals were O RH1-Negative, dce/rr. ConclusionIn conclusion these initial findings have demonstrated a decreased incidence of blood type O Rh1-negative in HIV + individuals which suggests that red blood cell antigens may play an important role in susceptibility to HIV infection. The relationship between red cell antigens and HIV infection however remains complex and therefore larger studies are required to confirm these results.

Downregulation of Glycosyltransferase a Expression By miRNA-331-3p Is Mediated By the Inhibition of the Transcription Factor SP1

More than 100 ABO subgroup-related variations were detected in the coding region of glycosyltransferases, which may be causative for a weak blood group antigen A or B expression. Most variation in expression is explained genetically by mutations that reduce transferase activity. However, a substantial number of weak variants have not yet been explained by current methods. We recently postulated a role of miRNA in the regulation of blood group A antigen expression levels. By using different approaches, including gene array analysis, luciferase reporter assay and overexpression of glycosyltransferase specific miRNAs in primary hematopoietic stem cells (HSCs), we found that miR-331-3p directly targets glycosyltransferase A and B mRNA. Now we have been further embarking on the underlying mechanisms of miRNA and glycosyltransferase interactions and show that the effects of miR-331-3p are mediated by inhibition of transcription factor SP1, which is a major regulator of the ABO gene, thereby resulting in downregulation of blood group A antigen expression in A2O individuals by up to 80% and in A1O individuals by up to 50%. Using microRNA target prediction tools we also identified Sp1 as a potential target gene for miR-331-3p. Western blot analyses of glycosyltransferase protein expression showed that overexpression of miR-331 led to a decreased glycosyltransferase and SP1 protein expression. Further approaches with the SP1 inhibitor, mithramycin A, revealed similar results. Analysis of Aw04/O1v genotypes revealed elevated miRNA levels, thus confirming microRNAs as regulators of blood group glycosyltransferase expression. Our findings extend our understanding of blood group regulation in carriers of weak blood group variants. Involvement of miRNAs in the downregulation of ABO blood group antigen expression may also provide an explanation for observed changes of ABO antigen expression in abnormal processes such as tumorigenesis, pregnancy and aging. Furthermore, this pathway may play a role in the regulation of other blood group variants (for instance Rhesus, KELL, amongst others). DisclosuresNo relevant conflicts of interest to declare.

Protein stability changes of the novel p.Arg180Cys mutant A glycosyltransferase resulted in a weak A phenotype.

A novel A subgroup allele (c.538C>T p.Arg180Cys) showing weak A phenotype was found in a 30-year-old Korean woman with ABO discrepancy. Using 3D structural analysis, protein stability prediction and flow cytometric analysis of ABO antigen expression on HeLa cells transfected with plasmids containing the p.Arg180Cys mutant, we found that the Arg180 residue in the loop region of the A glycosyltransferases (GTA) structure plays significant role in stabilizing its closed conformation, which is required for substrate binding and catalysis study.

ABO subgroup studies in Korea

Numerous examples of A or B subgroup alleles have been described in many geographical and ethnic groups. To analyse the phenotypic and genotypic basis of some ABO subgroups in Korea, a large‐scale study was performed on 169 605 samples from Korean blood donors. The overall incidence of ABO subgroups was 0·13% (227/169,605) in this donor population. Based on genotyping and/or serologic typing, the subgroups identified were as follows: A2B (n = 120), A2B3 (n = 36), A1B3 (n = 22), A2 (n = 13), B3 (n = 13), AintB3 (n = 6) and others (n = 17). Amongst these individuals with ABO subgroups, 26·4% (60/227) demonstrated a cis‐AB01 allele. It has been reported that the Korean population has several unique ABO subgroups (Aw10, Aw14 and B306) showing allelic competition or allelic enhancement. Several congenital blood chimaeras have been also found when studying individuals with ABO subgroups. Like ABO subgroups showing the allelic enhancement and allelic competition, chimaerism is also an important cause of ABO phenotype–genotype discrepancies when implementing DNA‐based blood grouping techniques. To understand the pattern of A and B antigen expression amongst donors with subtype alleles, flow cytometric analysis of ABO antigen expression on HeLa cells transfected with plasmids containing various mutants was used, in addition to ABO genotyping.

Red cell antigen loss in a patient with chronic myeloid leukemia: A case of ABO discrepancy

Change in ABO antigen expression on the surface of neoplastic cells have been seen for a variety of tumor types. This phenomenon has been linked with myeloid neoplasms as well but is reported infrequently. Here, we report a rare cause of ABO discrepancy in an elderly female having chronic myeloid leukemia.