Bach‐Nga Pham

Background The absence of expression of C/c and E/e antigens has been associated with rare variant RHCE alleles, referred to as silent RHCE alleles, classically identified among individuals with a rare D– – or Rh_null phenotype. This work reports on different molecular mechanisms identified in three novel silent RHCE alleles. Study Design and Methods Samples from D– – or Rh_null individuals and their family members, from families for whom Rh phenotype and/or serologic data were unexplained by inheritance of conventional RH alleles, were analyzed. Genomic DNA and transcripts were tested by sequencing analysis. Results The first silent allele was a RHCE*cE allele carrying an intronic IVS3+5G>A mutation. The second was a RHCE*ce allele carrying an intronic IVS7‐2A>G mutation, whereas the third was a silent RHCE*ce allele carrying a 5‐bp deletion (Nucleotides 679‐683) in Exon 5. Conclusion In addition to hybrid alleles and nucleotide deletion, intronic mutations may be associated with the nonexpression of RhCE antigens. Regarding the RH system, silent alleles may not be investigated among D– – or Rh_null individuals only. Rh phenotype and/or serologic data unexplained by inheritance of conventional RH alleles should lead to molecular investigations.

BACKGROUND: Drug‐dependent antibodies have been associated with approximately 10% of acquired immune hemolytic anemia cases. These antibodies are a rare cause of interference in pretransfusion red blood cell (RBC) serologic testing. The aim of this work was to report three cases of subjects developing antibodies against co‐trimoxazole, a combination of trimethoprim (TMP) and sulfamethoxazole (SMX).CASE REPORT AND METHODS: Blood samples of donor/patients were referred to our laboratory for the exploration of a positive antibody detection test. There was no recent history of drug taking. Antibody identification was performed by gel test using an indirect antiglobulin test, with reagent RBCs in low‐ionic‐strength solutions (LISS) containing co‐trimoxazole or not.RESULTS: All three sera showed positive reactions when RBCs were resuspended in LISS containing co‐trimoxazole, but negative reactions when RBCs were resuspended in LISS without antibiotic. We detected antibodies against co‐trimoxazole showing three different antibody patterns: anti‐TMP plus anti‐SMX, anti‐TMP alone, or anti‐SMX alone. Anti‐TMP showed an apparent anti‐Ku specificity in the two cases where it was present. Anti‐SMX showed an apparent anti‐H specificity in one of the two cases described. The drug‐dependent antibodies were not associated with acquired hemolytic anemia or other pathologies.CONCLUSION: Antibodies against co‐trimoxazole may only be detected when using a diluent for reagent RBCs containing the drug in question. Antibody pattern (anti‐TMP and/or anti‐SMX) may vary according to individuals' immune response. Drug‐dependent antibodies may react as antibodies against a high‐prevalence antigen, supporting the hypothesis of antibodies to drug and membrane components. Drug‐dependent antibodies such as anti‐co‐trimoxazole may be a serologic finding without clinical features.

BACKGROUND:Whether anti‐D produced by individuals with a weak D phenotype are allo‐ or autoantibodies remains a matter of debate even though blood transfusion practice is impacted. The aim of our study was to determine the serologic features of anti‐D in individuals expressing the most frequent weak D type in Caucasians that are weak D Type 1 or weak D Type 2, to assess whether anti‐D were allo‐ or autoantibodies.STUDY DESIGN AND METHODS:Serologic D typing and molecular analysis enabled the including of 121 weak D Type 1 individuals and 99 weak D Type 2 individuals in our study. Serologic features of anti‐D included autologous controls, direct antiglobulin test, elution, and titration of anti‐D before and after adsorption of serum on autologous red blood cells (RBCs).RESULTS:Serologic D typing showed a variable reactivity of RBCs expressing weak D Type 1 or weak D Type 2 (4+ to 0). Anti‐D was identified in six weak D Type 1 and six weak D Type 2 individuals, respectively. The serologic data were in favor of autoantibodies.CONCLUSION:A complete anti‐D investigation in individuals with a D variant (weak D or partial D identified by molecular analysis) should be systematically performed before any valid conclusion on the nature of the antibody. Transfusing weak D Type 1 or weak D Type 2 patients with D+ RBC units should be recommended. Weak D Type 1 or weak D Type 2 pregnant women do not need anti‐D immunoprophylaxis.

BACKGROUND: DNA testing has enabled the documenting of numerous variants of RHCE alleles, especially in individuals of African origin. The risk for production of clinically significant alloantibodies to Rh antigens of patients carrying variant RHCE alleles has led us to analyze the different RhCE variants investigated by molecular biology. Alloimmunization was analyzed regarding the RHCE genetic profile. STUDY DESIGN AND METHODS: Samples from 806 individuals with altered expression of RhCE antigens and/or producing anti‐RhCE in the presence of the corresponding antigen were analyzed. RESULTS: A total of 572 individuals were shown to express RhCE variants. Variant RHCE*ce alleles and RH haplotypes were identified in 83% of cases, the most frequent ones being the R^N haplotype, the ceMO allele, the (C)ce^s haplotype/ce^s1006 allele, and the ceAR allele identified in 36, 23, 20, and 17% of the tested samples, respectively. The absence of a high‐prevalence Rh antigen was documented in 93 individuals. Partial C and partial e were expressed by 53% of individuals with RhCE variants. Rh antibodies were identified in 127 (20%) of 623 patients. They were found to be alloantibodies in 48 (38%) of these 127 patients. Alloimmunization against a high‐prevalence Rh antigen was detected in 25% of cases. CONCLUSION: The challenge in clinical red blood cell (RBC) transfusion of patients with sickle cell disease, notably, would be to provide not only phenotypically matched, but also genetically matched, RBC units regarding RhCE variants.

BACKGROUND: The KN blood group system, which consists of nine antigen specificities, is located on complement receptor Type 1 (CR1/CD35). CR1, a complement regulatory protein, acts as a vehicle for immune complex clearance. CR1 exhibits a red blood cell (RBC) density polymorphism. CR1 sites on RBCs in normal individuals range from 150 to 1200 molecules per cell. CR1 density polymorphism is regulated by HindIII restriction fragment length polymorphism and Q981H and P1786R polymorphisms in Caucasians. Yet, the role of the different polymorphisms in determining the CR1 density on RBCs remains unknown. The “null” serologic KN phenotype, known as Helgeson phenotype, was reported to be related with a very low CR1 density, less than 150 molecules per cell.STUDY DESIGN AND METHODS: The aim of this work was to investigate whether the KN‐negative phenotype displayed by 60 individuals was related to the CR1 density by performing the phenotypic and genetic analysis of CR1 and to investigate the molecular background associated with the KN system.RESULTS: We showed that the Helgeson‐like phenotype had a prevalence of 12% in this population. The overall genotype/phenotype concordance was 90%. Among individuals with a KN‐negative phenotype, the prevalences of Kn(a–), McC(a–), Sl1‐negative, Sl3‐negative, and KCAM‐negative deduced phenotype were 37, 12, 29, 7, and 24%, respectively.CONCLUSION: From our data, we suggest that the definition of the Helgeson phenotype must be revised, since the latter may be due not only to a very low CR1 density on RBCs, but also to the absence of expression of a high‐prevalence KN antigen.

BACKGROUND: Since their description in the 1970s, anti‐Hr^B (antibody against a high‐prevalence Rh antigen) and anti‐hr^B (anti‐e–like antibody) are still a subject of debate about representing two aspects of a global immune response or being two independent antibodies.STUDY DESIGN AND METHODS: The aim of this study was to evaluate the immune response against the antigens of Rh system of 30 individuals presenting a hr^B(RH31)− phenotype. Genomic analysis of RH genes was performed in all individuals.RESULTS: Among the 30 individuals, 27 had a Hr^B(RH34)− phenotype. No immunization against Rh antigens was found in 16 individuals. Three individuals made anti‐D only, whereas six individuals made anti‐Hr^B (four with anti‐hr^B and two without anti‐hr^B) and two individuals made anti‐hr^B without anti‐Hr^B. Among the 30 individuals, three had a Hr^B+ phenotype. No immunization against Rh antigens was found in one individual, whereas two individuals made anti‐hr^B; the genomic analysis of selected individuals showed the presence of a (C)ce^s haplotype, either Type 1 or Type 2, and a DIII Type 5 ce^s haplotype, in the homozygous state, in compound heterozygosity with each other or in heterozygosity with a DcE haplotype. Genomic data were in accordance with serologic data.CONCLUSION: Our data provide the evidence that anti‐Hr^B and anti‐hr^B are independent antibodies, defining two different specificities. These antibodies may be produced by individuals expressing variants of RhCE protein. Serologic and molecular data indicate that e antigen encoded by the (C)ce^s haplotype is a partial antigen. In individuals carrying a (C)ce^s haplotype, the risk and the type of alloimmunization to Rh antigens are related to the second Rh haplotype.

BACKGROUND: In the Rh blood group system, published observations showed that the c antigen has the fewest variant forms of the principal antigens in this system. The partial nature of the c antigen was only reported in c+ Rh:−26 persons and to be associated with the ce^s(340) allele. This study reports the first case of alloanti‐c related to a (C)ce^s haplotype.STUDY DESIGN AND METHODS: Serologic and genetic studies were performed on blood samples of a multitransfused 40‐year‐old African patient with sickle cell disease displaying a DCcee phenotype.RESULTS: Red blood cells (RBCs) of the patient displayed normal expression of C, c, e, ce antigens either with routine reagents or with monoclonal antibodies. Analyses of DNA and Rh transcripts showed that the patient carried a (C)ce^s/DCe genotype. The patient's serum contained anti‐D, anti‐c, anti‐E, anti‐e, anti‐V, anti‐Js^a, and anti‐S. Anti‐c was isolated from the mixture of antibodies by using absorption and adsorption‐elution techniques. Anti‐c provided consistent reactions with c+ RBCs. Reactions were stronger with c+ ce+ RBCs than with c+ ce− RBCs. No agglutination of RBCs from individuals carrying a homozygous (C)ce^s genotype was observed.CONCLUSION: These data provide the evidence that anti‐c in our patient was an alloanti‐c and, consequently, that (C)ce^s haplotype encodes a partial c antigen. The clinical significance of anti‐c related to this haplotype should be evaluated in the future.