Characterization of Novel RHD Allele Variants and Their Implications for Routine Blood Group Diagnostics

The Rh system, including the highly immunogenic D antigen, is one of the clinically most important blood group systems in transfusion medicine. Numerous alleles of the RHD gene are associated with variant RhD phenotypes. In case of Rh incompatibility, some of them can induce hemolytic transfusion reactions and hemolytic disease of the fetus and newborn. Thus, accurate blood group diagnostics are critical for safe transfusion therapy. We characterized phenotypes of four individuals revealing weakened D expression during routine pre-transfusion testing. Standard gel card matrix techniques with monoclonal and polyclonal anti-D antibodies were used for serological typing, complemented using D epitope and antigen density analysis. Genotyping employing PCR with sequence-specific primers, genomic and allele-specific Sanger sequencing and in silico protein analysis were performed. Four novel RHD alleles associated with weak D or partial D phenotypes were identified. One of the mutations is predicted to disrupt the terminal stop codon and result in an elongated translation of the mutant D protein that phenotypically exhibits a loss of D epitopes. Furthermore, a hybrid gene formed with the homologue RHCE gene is described. The presented data enhances the understanding of the Rh system and may contribute to continued advances in blood group diagnostics.

Relationships of ABO and Rhesus blood groups with type 2 diabetes mellitus: a systematic review and meta-analysis

OBJECTIVES

The susceptibility to type 2 diabetes mellitus (T2DM) has been linked to blood type. We aimed to characterize the relationships of the ABO and Rhesus blood groups with T2DM.

METHODS

Literature searches were performed using the Medline, PubMed, Scopus, Cochrane, EMBASE, and Google Scholar databases to identify studies published up to 31 March 2022. The PRISMA guidelines were used for reporting. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were obtained using fixed-effects models.

RESULTS

Twenty-six studies of 6870 patients with T2DM and 11,879 controls were identified. Compared with the other ABO groups, people with blood type B were at higher risk of T2DM (OR: 1.30, 95% CI: 1.20-1.41), while group O was associated with a lower risk (OR: 0.92, 95% CI: 0.86-0.98). There were no significant associations of T2DM with blood types A or AB, or Rh factor.

CONCLUSION

Individuals with blood type B are at higher risk of developing T2DM. Therefore, they should be screened for T2DM on a frequent basis and be made aware of the importance of maintaining a balanced diet and regular exercise for the prevention of obesity and T2DM.

PROSPERO REGISTRATION NUMBER

CRD42022353945.

Rhesus blood group haplotype frequencies among blood donors in southwestern Uganda

Aim/objective

The study was undertaken to determine the Rhesus blood group system and Rhesus haplotype frequencies among blood donors at Mbarara Regional Blood Bank.

Materials and methods

We included ethylene-diaminetetra-acetic acid-containing plasma samples and serum samples from recruited consented blood donors. The Rh blood group system and the Rh haplotypes was established by the incubation of appropriate antisera (anti-D, anti-E, anti-C, anti-e, and anti-c) and cells at a temperature of 24°C in microplates for 1 hour and the reaction was read by gentle shaking and examining for agglutinations. Donors were asked to fill in questionnaires, after we obtained the informed consent, to assess their demographics.

Results

Among the 386 participants, 233 were males (60%) and 153 (40%) females. The Rh negative blood group percentage was 3.8%, while the Rh haplotype frequencies were as follows: Dce dce 68.1%, dce dce 2.8%, CD. dce 13%, cDE dce 12.4%, DC. DcE 1.6%, DcE DcE 1%, dC. dce 0.8%, and DcE DC. 0.3%.

Conclusion

Given this frequency, a high prevalence of anti-D alloantibody formation among those transfused is possible and could cause diverse effects, especially in the Rh D positive women. We recommend additional research studies on the role of autoimmunity to the transfused on the occurrence of Rh D variants plus their implications on hemolytic disease of the fetus and newborn in Uganda. This study recommends that the blood bank includes Rhesus haplotyping in its protocols and that the finding be disseminated to donors and blood users.

Hemolytic disease of the fetus and newborn in the molecular era

Maternal-fetal red cell antigen incompatibility can lead to alloimmunization, maternal immunoglobulin transplacental transfer, and hemolytic disease of the fetus and newborn (HDFN). The use of routine antenatal anti-D prophylaxis (RAADP) has sharply decreased the incidence of and mortality from HDFN due to RhD allosensitization. The ability to identify pregnancies/fetuses at risk of HDFN has significantly improved due to paternal molecular RHD zygosity testing, and non-invasive fetal molecular diagnostics for detecting putative antigen(s) (notably RhD) in fetuses utilizing cff-DNA in maternal plasma. Fetal RHD genotyping using cff-DNA has become increasingly accurate for fetal RHD detection, prompting some countries to implement targeted RAADP through mass screening programs of RhD-negative pregnant women. Along with middle cerebral artery Doppler ultrasonography for predicting fetal anemia, non-invasive fetal molecular diagnostics have greatly decreased the need for invasive diagnostic procedures in pregnancies at risk for severe HDFN. This review highlights these molecular advancements in HDFN-related prenatal diagnostics.