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

Autoimmune anti-D in an RhD-positive young infant: Learning from a rare case

BACKGROUND AND OBJECTIVES

Anti-D is usually immune in nature and is formed in individuals lacking D antigen or having variants/altered D phenotypes. In the Indian population, 93.8% are RhD positive, and R1 R1 is the commonest Rh phenotype. Here we report a rare and interesting case of autoimmune anti-D in an RhD-positive 3-month-old infant leading to warm autoimmune haemolytic anaemia.

STUDY DESIGN AND METHODS

Auto-anti-D was detected serologically by immunohaematological techniques such as direct antiglobulin test, antibody detection and identification, dithiothreitol, enzyme treatment, antibody titration and elution. Molecular studies were performed to rule out genetic variants of RhD.

RESULTS

Anti-D was confirmed in eluate and blood group post elution was B RhD positive. On genotyping using the Indian-specific RHD genotyping assay, the sample was found to be negative for the RHD*01W.150 (most common RhD variant in Indians) but positive for RHD exon 5 and RHD exon 10 along with glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The sample was further sequenced for RHD exons 1-10 by Sanger sequencing and found to be a wild type, thus, ruling out the presence of an RhD variant.

CONCLUSION

This case is of interest because of the rare occurrence of autoimmune anti-D in an RhD-positive patient of such a young age (3 months). To the best of our knowledge, only two case reports have been published on autoimmune anti-D in infancy (in 1961 and 1964).

Transfusion management of Africans with RHD variants in China

The presence of D variant among minorities could produce a higher rate of alloimmunization observed in patients from this group. This is partly due to the ethnic and racial specificity of RHD variants and the limited availability of Rh-matched blood donors. Approximately half a million African migrants in China carrying distinct Rh blood type composition have presented to the health care system with an imperative safety requirement of blood transfusion among 1.3 billion Chinese individuals. We depict the clinically significant RHD alleles among African migrants living in China and identify the genetic similarities and disparities to Chinese. We discussed practical strategies to manage the unique transfusion needs of African migrants in China.

RHD and RHCE molecular analysis in weak D blood donors and in patients with Rh antibodies against their own corresponding Rh antigen

BACKGROUND

The Rh system is the largest and most polymorphic blood group system. The existence of a large number of RH alleles results in variant phenotypes that often complicate blood donor phenotyping and the distinction between auto- and allo-antibodies in recipients who have anti-Rh antibodies in the presence of their own corresponding Rh antigen. Knowledge of these variants is necessary in order to make blood transfusion safer.

MATERIALS AND METHODS

Samples from 48 blood donors with serological weak D and from 29 patients who had anti-Rh antibody in the presence of their own corresponding Rh antigen were evaluated molecularly for RHD and RHCE alleles using a blood-multiplex ligation-dependent probe amplification assay and Sanger sequencing.

RESULTS

Rh variants were found in 45 of the 48 blood donors: 24/45 (53%) were weak D, 2/45 (4%) partial D and 19/45 (42%) were weak and partial D. The remaining three donors (6%) did not show a mutation in the RHD allele. Among the 29 patients, 13/29 had anti-e, of whom 4/13 had genotypes that predicted a partial e antigen; 11/29 had anti-D, with 6/11 being identified as partial D; 2/29 had anti-c, of whom 1/2 was predicted to express partial c antigen; 4/29 who had anti-E and 4/29 who had anti-C did not show mutations in RHCE*C or RHCE*E.

DISCUSSION

It was possible to find individuals with clinically significant Rh phenotypes due to the weak reactivity of the D antigen, detected through serological tests in blood donors. In patients, when found with the anti-Rh antibody in the presence of the same Rh antigen, it is difficult to distinguish an auto-antibody from an allo-antibody by serological tests; in these cases, molecular methods (genotyping) can help us to determine whether there are changes in the RH alleles and to discover the nature of the antibody (allo or auto).

Transfusion strategy for weak D Type 4.0 based on RHD alleles and RH haplotypes in Tunisia

BACKGROUND

With more than 460 RHD alleles, this gene is the most complex and polymorphic among all blood group systems. The Tunisian population has the largest known prevalence of weak D Type 4.0 alleles, occurring in one of 105 RH haplotypes. We aimed to establish a rationale for the transfusion strategy of weak D Type 4.0 in Tunisia.

STUDY DESIGN AND METHODS

Donors were randomly screened for the serologic weak D phenotype. The RHD coding sequence and parts of the introns were sequenced. To establish the RH haplotype, the RHCE gene was tested for characteristic single-nucleotide positions.

RESULTS

We determined all RHD alleles and the RH haplotypes coding for the serologic weak D phenotype among 13,431 Tunisian donations. A serologic weak D phenotype was found in 67 individuals (0.50%). Among them, 60 carried a weak D Type 4 allele: 53 weak D Type 4.0, six weak D Type 4.2.2 (DAR), and one weak D Type 4.1. An additional four donors had one variant allele each: DVII, weak D Type 1, weak D Type 3, and weak D type 100, while three donors showed a normal RHD sequence. The weak D Type 4.0 was most often linked to RHCE*ceVS.04.01, weak D Type 4.2.2 to RHCE*ceAR, and weak D Type 4.1 to RHCE*ceVS.02, while the other RHD alleles were linked to one of the common RHCE alleles.

CONCLUSIONS

Among the weak D phenotypes in Tunisia, no novel RHD allele was found and almost 90% were caused by alleles of the weak D Type 4 cluster, of which 88% represented the weak D Type 4.0 allele. Based on established RH haplotypes for variant RHD and RHCE alleles and the lack of adverse clinical reports, we recommend D+ transfusions for patients with weak D Type 4.0 in Tunisia.

Clinically relevant RHD-CE genotypes in patients with sickle cell disease and in African Brazilian donors

BACKGROUND

As a consequence of the homology and opposite orientation of RHD and RHCE, numerous gene rearrangements have occurred in Africans and resulted in altered RH alleles that predict partial antigens, contributing to the high rate of Rh alloimmunisation among patients with sickle cell disease (SCD). In this study, we characterised variant RH alleles encoding partial antigens and/or lacking high prevalence antigens in patients with SCD and in African Brazilian donors, in order to support antigen-matched blood for transfusion.

MATERIAL AND METHODS

RH genotypes were determined in 168 DNA samples from SCD patients and 280 DNA samples from African Brazilian donors. Laboratory developed tests, RHD BeadChip(TM), RHCE BeadChip(TM), cloning and sequencing were used to determine RHD-CE genotypes among patients and African Brazilian blood donors.

RESULTS

The distributions of RHD and RHCE alleles in donors and patients were similar. We found RHCE variant alleles inherited with altered RHD alleles in 25 out of 168 patients (15%) and in 22 out of 280 (7.8%) African Brazilian donors. The RHD and RHCE allele combinations found in the population studied were: RHD*DAR with RHCE*ceAR; RHD*weak D type 4.2.2 with RHCE*ceAR, RHD*weak D type 4.0 with RHCE*ceVS.01 and RHCE*ceVS.02; RHD*DIIIa with RHCE*ceVS.02. Thirteen patients and six donors had RHD-CE genotypes with homozygous or compound heterozygous alleles predicting partial antigens and/or lacking high prevalence antigens. Eleven patients were alloimmunised to Rh antigens. For six patients with RHD-CE genotypes predicting partial antigens, no donors with similar genotypes were found.

DISCUSSION

Knowledge of the distribution and prevalence of RH alleles in patients with SCD and donors of African origin may be important for implementing a programme for RH genotype matching in SCD patients with RH variant alleles and clinically significant Rh antibodies.

Variant RHD Types in Brazilians With Discrepancies in RhD Typing

BACKGROUND

The knowledge of D variants in patients and donors is important because anti-D alloimmunization can occur in some but not all individuals who express a variant RHD allele. Serologic distinction of RhD discrepancies is not always straightforward, which makes molecular analysis highly desirable.

METHODS

A group of 223 subjects, 129 patients, and 94 blood donors was identified and analyzed on the basis of a D typing discrepancy. The D antigen expression was evaluated by tube and gel hemagglutination with four anti-D reagents. PCR-single specific primer (SSP), multiplex PCR, RHD BeadChip (Immucor), or sequencing were used for molecular analysis.

RESULTS

In total, 168/223 (75%) weak D and 55/223 (25%) partial D variants were identified. Hemagglutination results varied in methods and anti-D reagents used in this process. There was no standard serologic reactivity identified, which could predict what type of D variant would be identified. Among weak D samples, types 1-3 were the most common, while DAR and DVI were most prevalent among partial D samples.

CONCLUSION

Our results show that discrepancies found in the serologic typing should be investigated by molecular methods in order to determine the D variant involved and also to distinguish between weak D and partial D. The knowledge of the distribution of weak D types and partial D among populations is important for D- patients and pregnant women management.