Anti-D alloimmunization produced by apparently D negative red blood cells

TRUCCO BOGGIONE, CAROLINA; LUJÁN BRAJOVICH, MELINA ELIANA; MATTALONI, STELLA MARIS; RUCCI, ANGEL; GARCIA BORRAS, SILVIA; BIONDI, CLAUDIA; COTORRUELO, CARLOS

Mar del Plata

Congreso; LIX Reunión Científica Anual de la Sociedad Argentina de Investigación Clínica (SAIC). LXII Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2014

SAIC-SAI

The Rh system is highly polymorphic and one of the most clinically significant blood group in transfusion medicine. Reliable routine D typing approaches should be performed to identify some D variants that can cause anti-D alloimmunization upon transfusion. However, extremely weak D expression, termed DEL, may be confound from truly D negative units and used for D negative recipients. The aim of this study was to investigate the molecular basis of the RH locus in a serologically D negative donor whose red blood cells were responsible for anti-D immunization in a D negative patient. The donor´s Rh phenotype was performed using monoclonal antibodies and showed the expression of the c, E and e antigens. DNA was initially screened using a multiplex PCR strategy that amplifies intron 4 and the 3? untranslated region of the RHD gene and revealed the presence of a RHD allele. Molecular analyses based on exon scanning, microarray and sequencing allowed the detection of a 46T>C mutation in exon 1 of RHD gene, which produces the W16R change. Further serological characterization confirmed an extremely weak expression of the D antigen. In silico 3D structure analysis of the RhD protein showed that the aminoacid change was located in the predictive first transmembrane helix. The introduction of a charged residue in this position is likely to be disruptive giving rise to steric hindrance affecting the global fold of the RhD polypeptide and altering D expression. To estimate the frequency of this new allele, a screening of 114 D-, C/E+ samples was performed. This mutation was found in 13.2% of the D-, E+ samples only, suggesting that this clinically important variant is associated with E antigen. The high incidence of this DEL allele in our population highlights the importance of genotyping D-, E+ donors to properly detect samples with a diminished D antigen expression to avoid alloimmunization.