Molecular basis of DEL phenotype in the Chinese population.

BACKGROUND: Rh blood group system is the most complex and immunogenetic blood group system. Prevalent RHD alleles vary in different populations. We conducted the present study to examine the genotype of DEL individuals and to elucidate whether novel alleles exist in the Chinese population. METHODS: DEL phenotype was identified by a serologic adsorption-elution method. The nucleotide sequences of ten RHD exons and exon-intron boundary regions were evaluated by RHD gene-specific PCR-SSP and sequencing. RESULTS: Of 42306 samples from individual donors and patients, 165 samples were typed as D-negative. Among these D-negative samples, 41 DEL individuals were observed. Thirty-seven DELs were confirmed to have the RHD1227A allele. Two DELs seemed to have RHD-CE-D hybrid alleles, including one RHD-CE (4-7)-D and one RHD-CE (2-5)-D. Two novel RHD alleles were found among the rest of the DEL samples, including one RHD93T > A and one RHD838G > A. CONCLUSION: In this study, about 24.85% (41/165) of the apparent D-negative Chinese individuals were DEL. RHD1227G > A is the most frequent allele in Chinese DEL phenotypes, accounting for 90.24% (37/41). The RHD-CE-D hybrid allele might be the second most frequent DEL allele in the Chinese population. Our study would contribute to the understanding of the molecular mechanism underlying D antigen expression of DEL individuals and provide useful information for designing suitable genotyping strategies in RhD-negative individuals in Asia.

Analysis of density and epitopes of D antigen on the surface of erythrocytes from DEL phenotypic individuals carrying the RHD1227A allele.

BACKGROUND: The characteristics of the D antigen are important as they influence the immunogenicity of D variant cells. Several studies on antigenic sites have been reported in normal D positive, weak D and partial D cases, including a comprehensive analysis of DEL types in Caucasians. The aim of this study was to assess D antigen density and epitopes on the erythrocyte surface of Asian type DEL phenotypic individuals carrying the RHD1227A allele in the Chinese population. MATERIALS AND METHODS: A total of 154 DEL phenotypic individuals carrying the RHD1227A allele were identified through adsorption and elution tests and polymerase chain reaction analysis with sequence-specific primers in the Chinese population. D antigen density on the erythrocyte surface of these individuals was detected using a flow cytometric method. An erythrocyte sample with known D antigen density was used as a standard. Blood samples from D-negative and D-positive individuals were used as controls. In addition, D antigen epitopes on the erythrocyte surface of DEL individuals carrying the RHD1227A allele were investigated with 18 monoclonal anti-D antibodies specific for different D antigen epitopes. RESULTS: The means of the median fluorescence intensity of D antigen on the erythrocyte membrane surface of D-negative, D-positive and DEL individuals were 2.14±0.25, 193.61±11.43 and 2.45±0.82, respectively. The DEL samples were estimated to have approximately 22 D antigens per cell. The samples from all 154 DEL individuals reacted positively with 18 monoclonal anti-D antibodies specific for different D antigen epitopes. DISCUSSION: In this study, D antigen density on the erythrocyte surface of DEL individuals carrying the RHD1227A allele was extremely low, there being only very few antigenic molecules per cell, but the D antigen epitopes were grossly complete.

An investigation of secondary anti-D immunisation among phenotypically RhD-negative individuals in the Chinese population.

BACKGROUND: Despite the introduction of anti-D prophylaxis into clinical practice, RhD alloimmunisation remains a problem, particularly in the context of transfusions and pregnancy-induced alloimmunisation. The incidence of RhD alloimmunisation among phenotypically RhD-negative individuals is unknown in most countries. We investigated RhD alloimmmunisation in RhD-negative pregnant women and transfusion recipients in south-east China in order to optimise the prevention of this phenomenon. METHODS: We analysed the RhD alloimmunisation status of RhD-negative pregnant women and transfusion recipients in south-east China. The RhD blood types of the study population were identified by standard serological methods. The D antigen was further tested with the indirect antiglobulin test to exclude or confirm weak D or partial D types. RhC, c, E and e antigens were typed in all subjects. If anti-D antibody screening was positive, the specificity and titre of the antibody were determined. The Del phenotype was investigated by the polymerase chain reaction sequence-specific primer method. RESULTS: An anti-D antibody was found in 61 of 416 RhD-negative pregnant women (14.66%), and in 11 of 227 RhD-negative transfusion recipients (4.85%). None of the 72 RhD-negative pregnant women or transfusion recipients with anti-D had the Del phenotype. Anti-D antibodies were not detected among Del phenotype individuals and Del phenotypes were not found in anti-D antibody producing individuals. DISCUSSION: Our study suggests that the risk of alloimmunity-induced neonatal haemolysis increases in true RhD-negative multipara. Perinatal protection would be necessary in these patients, while antenatal anti-D testing and Rh immune globulin prophylaxis would be unnecessary for RhDel pregnant women. Pregnant women and transfusion recipients with the Del type seldom produce anti-D antibody. RhD-negative recipients are not at risk of alloimmunisation after transfusion with Del red blood cells.

Survivin up-regulates the expression of breast cancer resistance protein (BCRP) through attenuating the suppression of p53 on NF-κB expression in MCF-7/5-FU cells.

Both breast cancer resistance protein (BCRP, ABCG2) and apoptosis-related molecules are involved in the development of multidrug resistance (MDR) in cancer cells. However, the association of BCRP with apoptosis-related molecules in the development of MDR is unknown. In this study, we investigated the changes in expression levels of BCRP, Survivin, p53, Bcl-2, Bcl-xL or Bax in cultured MCF-7 and MCF-7/5-FU cells, and explored whether these changes affected the expressions of BCRP. Our data showed that the protein and mRNA expression levels of BCRP, Survivin and Bcl-2 were significantly higher in MCF-7/5-FU cells than in MCF-7 cells, while p53 expression lower in MCF-7/5-FU cells than in MCF-7 cells. Knockdown of Survivin or Bcl-2 in MCF-7/5-FU cells and overexpression of Survivin in MCF-7 cells revealed that Survivin had significant association with BCRP expression. Luciferase reporter gene assays showed that Survivin up-regulated BCRP expression at transcriptional level and this response was mediated through NF-κB(p50) pathway. However, may be due to the physical interaction between p53 and Survivin, p53 directly affected Survivin-regulated BCRP expressions. Interestingly, we found that Survivin would suppress p53 expression. Furthermore, our data revealed that Survivin itself had no apparent effect on NF-κB(p50) and BCRP expression when knockdown of p53 in MCF-7 cells; whereas p53 exerted significant inhibitory action on these when knockdown of Survivin. In conclusion, through down regulation of p53 expression, Survivin attenuates the suppressing effect of p53 on NF-κB(p50) expression and then enhances BCRP expression. This may represent a novel strategy for reversal of BCRP drug transporter activity to modulate MDR in cancer cells.