The Duffy blood group system in the Tunisian population.

BACKGROUND: Tunisia was described to as genetically heterogenous. Besides the 1% native Berber, the genetically influence of the Europeans seems much larger than that of sub-Saharan populations. Due to their ethnic variability, blood group variants have the potential to support population analyses. The aim of this study was to estimate the Duffy blood group system in this mixed population with enhanced characterization of samples with aberrant expression. MATERIALS AND METHODS: Standard serological testing for the Duffy antigen was done for 105 Tunisian blood donors. Samples with altered Fy expression underwent DNA sequencing of the DARC, RHD and RHCE genes. RESULTS: The Fy(a-b+) was the most common phenotype identified in the Tunisian population (38.1%). Five samples with Fy(a-b-) phenotype were determined as FY*02N.01/FY*02N.01 by a homozygous occurrence of the FY*B-67C>T alteration. Another three individuals exhibited a Fy(b+(w))Fy(x) expression, confirmed by a FY*A/FY*02M.01 (n = 1) and a FY*02M.01/FY*02M.01 (n = 2) genotype. RHD and RHCE sequencing (n= 8) revealed altered alleles observed in black populations in 5 samples. One individual with FY*02M.01/FY*02M.01 have the silent 165C>T nucleotide substitution each in the RHD and RHCE gene. DISCUSSION: The composition of blood group variants determined in this study confirms the genetically proximity of Tunisia to Europe. The small sub-Saharan genetic influence was approved by a limited number of variant samples associated with the black population.

Anti-D auto-immunization in a patient with weak D type 4.0.

We report the case of a 56-year-old patient with blood group O+C-c+E-e+K-, followed for a myelodysplasic syndrome and treated by regular pheno-identical and compatible (RBCs) transfusion since December 2007. In June 2009, a positive crossmatch was found with 2 RBCs O+C-c+E-e+K-. A positive anti-body screening with a positive autocontrol was detected and anti-D was unidentified in the patient's serum. The DAT was positive (IgG) and elution identified an anti-D. The following assumptions were then made: it could be a partial D phenotype with anti-D alloantibodies or RH: 1 phenotype with an anti-D auto-antibodies. Molecular analysis by multiplex PCR and sequencing have depisted a weak D type 4.0 phenotype. In October 2009, over three months of RH:-1 RBC transfusion, the antibody screening and DAT (IgG) remained positive, and an eluate made from the patient's erythrocytes contained an anti-D. All these funding confirmed the autoimmune nature of the anti-D. This case report illustrates the importance of a well-conducted and immunohematological laboratories test in order to distinguish between auto- or allo-immune of anti-D in a RH: 1 poly-transfused patients. This distinction is of great importance for transfusion support.

RHD*weak partial 4.0 is associated with an altered RHCE*ce(48C, 105T, 733G, 744C, 1025T) allele in the Tunisian population.

BACKGROUND AND OBJECTIVES: D is the most immunogenic blood group antigen. About 1% of whites carry an altered RHD allele leading to quantitative or qualitative changes in the antigen D expression. T201R and F223V encoded by 602C>G and 667T>G are specific amino acid substitutions of the weak D type 4 cluster of African origin, comprising the alleles RHD*09.01, RHD*09.02, RHD*09.03, RHD*09.04 and RHD*09.05. The purpose of this study was to estimate the presence of these RHD genotypes in the Tunisian population. MATERIALS AND METHODS: Ethylenediaminetetraacetate blood samples from 907 D+ and 93 D- blood donors were tested for markers 602G and 667G by allele-specific primer-polymerase chain reaction (PCR-ASP). Samples with positive reactions were re-evaluated by DNA sequencing for RHD and RHCE exons 1-10 and adjacent intronic sequences. RESULTS: Among 907 D+ samples, 19 individuals were identified to harbour the RHD*weak partial 4.0 allele. RHCE sequencing post-haplotype-specific extraction (HSE) revealed an altered RHCE*ce(48C, 105T, 733G, 744C, 1025T) in those samples. The linkage of the RHCE polymorphisms to one haplotype was proven by DNA sequencing post-HSE. CONCLUSION: The RHD*weak partial 4.0 allele syn. RHD*09.03 was estimated to occur 1 in 47 among D+ Tunisians. There was no evidence for other RHD alleles included in the weak D type 4 cluster.

[System RH: screening of partials D with RHD/RHCE hybrid gene]. / Système RH : dépistage de D partiels avec RHD/RHCE gène hybride.

AIM OF THE STUDY: The determination of the RhD phenotype is important in transfusion medicine. However, the complexity of the expression of the D antigen is the cause of the discrepancies observed between two serological determinations and the omission by serology of some variants that can be cause alloimmunization. Therefore, it is important to known in a population the RHD alleles responsible for partial D and weak D phenotype. The aim of the study was the screening of partial D with RHD/RHCE gene hybrid by PCR-multiplex. MATERIALS AND METHODS: Our study involved 308 blood donors from Tunisian Sahel (269 D positive and 39 D negative). We used the multiplex PCR assay to amplify specific exons of the RHD gene 3, 4, 5, 6, 7, 9 and 10. Further molecular investigations were carried to characterize the RHD variants that were detected by the multiplex. RESULTS: In the 269 D positive samples, one case showed the absence of amplification of exons 4 and 5 of RHD gene. This variant was identified by PCR-SSP on weak D type 4. None of the RHD exons were amplified from DNA of 39 D negative samples in favor of a total deletion of the RHD gene. CONCLUSION: We have no found any partial D variant with RHD/RHCE gene hybrid. Results in D negative samples showed that RHD gene deletion is the most frequent mechanism of D negative phenotype in the Tunisian population.