Sunitha Vege

High prevalence of red blood cell alloimmunization in sickle cell disease despite transfusion from Rh-matched minority donors

Red blood cell (RBC) transfusion is a key treatment of patients with sickle cell disease (SCD) but remains complicated by RBC immunization. In the present study, we evaluated the effects of antigen matching for Rh D, C, and E, and K and transfusion from African American donors in 182 patients with SCD. Overall, 71 (58%) chronic and 9 (15%) episodically transfused patients were alloimmunized. Fifty-five (45%) chronic and 7 (12%) episodically transfused patients were Rh immunized. Of 146 antibodies identified, 91 were unexplained Rh antibodies, one-third of which were associated with laboratory evidence of delayed transfusion reactions. Fifty-six antibodies occurred in patients whose RBCs were phenotypically positive for the corresponding Rh antigen and 35 in patients whose RBCs lacked the antigen and were transfused with Rh-matched RBCs. High-resolution RH genotyping revealed variant alleles in 87% of individuals. These data describe the prevalence of Rh alloimmunization in patients with SCD transfused with phenotypic Rh-matched African American RBCs. Our results suggest that altered RH alleles in both the patients and in the donors contributed to Rh alloimmunization in this study. Whether RH genotyping of patients and minority donors will reduce Rh alloimmunization in SCD needs to be examined.

DIIIa and DIII Type 5 are encoded by the same allele and are associated with altered RHCE*ce alleles: clinical implications

BACKGROUND: The partial D phenotype DIIIa was originally reported to be associated with 455A>C in Exon 3, 602C>G in Exon 4, and 667T>G in Exon 5. Other alleles with these changes were subsequently identified and designated DIII Types 5, 6, and 7, as they had additional alterations. The observation that DNA samples associated with the DIIIa phenotype had more changes than those originally reported motivated us to reanalyze the DIIIa probands (BP and DJ) from the original study. We also studied additional DIIIa samples to clarify the RHD background and establish the associated RHCE.

Changing practice: red blood cell typing by molecular methods for patients with sickle cell disease

Extended red blood cell (RBC) antigen matching is recommended to limit alloimmunization in patients with sickle cell disease (SCD). DNA‐based testing to predict blood group phenotypes has enhanced availability of antigen‐negative donor units and improved typing of transfused patients, but replacement of routine serologic typing for non‐ABO antigens with molecular typing for patients has not been reported.

RHCE*ceCF encodes partial c and partial e but not CELO, an antigen antithetical to Crawford

BACKGROUND: RH43 (Crawford) is encoded by RHCE*ce with nucleotide changes 48G>C, 697C>G, and 733C>G (RHCE*ceCF). We investigated the Rh antigen expression and antibody specificities in four patients with this allele.

The JAL antigen (RH48) is the result of a change in RHCE that encodes Arg114Trp

BACKGROUND: The JAL antigen (Rh48) was discovered more than 30 years ago when it caused hemolytic disease of the fetus and newborn in an African American family. A decade later it was found to cause hemolytic disease of the fetus and newborn in a Caucasian family. The presence of the same low‐prevalence antigen in two different ethnic groups is rare, but additional JAL+ in both groups was subsequently identified. This study was undertaken to investigate the RH gene(s) responsible for expression of JAL and to determine the structural relationship between JAL and other Rh antigens.

Whole-exome sequencing for RH genotyping and alloimmunization risk in children with sickle cell anemia.

RH genes are highly polymorphic and encode the most complex of the 35 human blood group systems. This genetic diversity contributes to Rh alloimmunization in patients with sickle cell anemia (SCA) and is not avoided by serologic Rh-matched red cell transfusions. Standard serologic testing does not distinguish variant Rh antigens. Single nucleotide polymorphism (SNP)-based DNA arrays detect many RHD and RHCE variants, but the number of alleles tested is limited. We explored a next-generation sequencing (NGS) approach using whole-exome sequencing (WES) in 27 Rh alloimmunized and 27 matched non-alloimmunized patients with SCA who received chronic red cell transfusions and were enrolled in a multicenter study. We demonstrate that WES provides a comprehensive RH genotype, identifies SNPs not interrogated by DNA array, and accurately determines RHD zygosity. Among this multicenter cohort, we demonstrate an association between an altered RH genotype and Rh alloimmunization: 52% of Rh immunized vs 19% of non-immunized patients expressed variant Rh without co-expression of the conventional protein. Our findings suggest that RH allele variation in patients with SCA is clinically relevant, and NGS technology can offer a comprehensive alternative to targeted SNP-based testing. This is particularly relevant as NGS data becomes more widely available and could provide the means for reducing Rh alloimmunization in children with SCA.

A DOB allele encoding an amino acid substitution (Phe62Ser) resulting in a Dombrock null phenotype

BACKGROUND: The gene polymorphisms responsible for the antigens Doa, Dob, Hy, and Joa in the Dombrock (Do) blood group system have been identified. Four different mutations have been reported to cause the Dombrock null [Gy(a–)] phenotype. These include splice mutations, an eight‐nucleotide deletion, and insertion of a stop codon. Here a Dombrock null caused by a single‐amino‐acid substitution in the full‐length protein is reported.

RHCE*ceMO is frequently in cis to RHD*DAU0 and encodes a hr(S) -, hr(B) -, RH:-61 phenotype in black persons: clinical significance.

RHCE*ceMO has nucleotide changes 48G>C and 667G>T, which encode, respectively, 16Cys and 223Phe associated with altered expression of e antigen. RHD*DAU0 has Nucleotide 1136C>T, which encodes 379Met associated with normal levels of D. We compiled serologic and DNA testing data on samples with RHCE*ceMO to determine the red blood cell (RBC) antigen expression, antibody specificity, RHD association, and the prevalence in African‐American persons.

RHCE*ceTI encodes partial c and partial e and is often in cis to RHD*DIVa

BACKGROUND: In the Rh blood group system, variant RhD and RhCE express several partial antigens. We investigated RH in samples with partial DIVa that demonstrated weak and variable reactivity with anti‐C.

A novel JKA allele, nt561C>A, associated with silencing of Kidd expression

BACKGROUND: The Jk(a−b−) null phenotype is not common but is more prevalent in Polynesian and Asian persons and appears to be rare in blacks. We determined the molecular basis for Jk(a−b−) in an African American family. DNA testing of samples from random African American, Caucasian, and Brazilian blacks was done to estimate the allele frequency.