Autoantibodies with Mimicking Specificity Detected by the Dilution Technique in Patients with Warm Autoantibodies

BACKGROUND: The aim of this study was to investigate the frequency of autoantibodies with mimicking specificity by using the dilution technique, to assess the usefulness of the combination of the dilution technique and red blood cell (RBC) phenotyping, and to establish a pre-transfusion testing algorithm in patients with warm autoantibodies. METHODS: Serum samples from 71 patients with warm autoantibodies were tested using the dilution technique. Among them, 25 samples were adsorbed with allogeneic ZZAP (a combination of dithiothreitol and enzyme) or polyethylene glycol (PEG) and their RBC phenotypes were determined. Thirty-nine patients were transfused with our pre-transfusion testing algorithm using a combination of dilution technique and RBC phenotyping. RESULTS: Autoantibodies with mimicking specificity were detected by the dilution technique in 26.8% (19/71) of the patients and most of them were directed against Rh system antigens. The agreement of the results obtained with the dilution technique in combination with RBC phenotyping and those from ZZAP or PEG adsorption was 100% (18/18) in patients who have autoantibodies with mimicking specificity and/or alloantibodies. No clinical symptoms indicating severe acute or delayed hemolytic transfusion reactions were reported in the 39 patients transfused with our pre-transfusion testing algorithm. CONCLUSIONS: Autoantibodies with mimicking specificity detected by the dilution technique in patients with warm autoantibodies are relatively frequent, can be discriminated from alloantibodies by employing a combination of dilution technique and RBC phenotyping, and might not appear to cause severe acute or delayed hemolytic transfusion reactions.

The M142T Mutation Causes B3 Phenotype: Three Cases and an in vitro Expression Study / 대한진단검사의학회지

The B3 phenotype is the most common B subtype in Korea. The B305 allele (425 T>C, M142T) was first reported in 2 Chinese individuals; however, it has not yet been reported in the Koreans, and the impact of the M142T mutation on the expression of the B3 phenotype has also not been studied. To resolve an ABO discrepancy between a group O neonate and her group O father and A(1)B(3) mother, blood samples from these individuals and other family members were referred to our laboratory for ABO gene analysis. The B305 allele was discovered in the neonate (B305/O01), her mother (A102/ B305), and her maternal aunt (B305/O02), while her father was typed as O01/O02. Transient transfection experiments were performed in HeLa cells using the B305 allele synthesized by site-directed mutagenesis; flow cytometric analysis revealed that this transfect expressed 35.5% of the total B antigen produced by the B101 allele transfect. For comparison, Bx01 allele transfects were also created, and they expressed 11.4% of the total B antigen expressed on the surface of B101 transfects. These experiments demonstrate that the M142T (425 T>C) mutation is responsible for the B subtype phenotype produced by the B305 allele.

A Dispermic Chimera with Mixed Field Blood Group B and Mosaic 46,XY/47,XYY Karyotype

Chimerism in humans is a rare phenomenon often initially identified in the resolution of an ABO blood type discrepancy. We report a dispermic chimera who presented with mixed field in his B antigen typing that might have been mistaken for the B3 subtype. The propositus is a healthy Korean male blood donor. Neither his clinical history nor initial molecular investigation of his ABO gene explained his mixed field agglutination with murine anti-B. Chimerism was suspected, and 9 short tandem repeat (STR) loci were analyzed on DNA extracted from blood, buccal swabs, and hair from this donor and on DNA isolated from peripheral blood lymphocytes from his parents. The propositus' red blood cells demonstrated mixed field agglutination with anti-B. Exon 6 and 7 and flanking intronic regions of his ABO gene were sequenced and revealed an O01/O02 genotype. B allele haplotype-specific PCR, along with exon 6 and 7 cloning and sequencing demonstrated a third ABO allele, B101. Four STR loci demonstrated a pattern consistent with a double paternal chromosome contribution in the propositus, thus confirming chimerism. His karyotype revealed a mosaic pattern: 32/50 metaphases were 46,XY and 18/50 metaphases demonstrated 47,XYY.