Official Journal of the British Blood Transfusion Society Transfusion Medicine | ORIGINAL ARTICLE RHCE variants inherited with altered RHD alleles in Brazilian blood donors C. Prisco Arnoni, 1 J. Guilhem Muniz, 1 T. A. de Paula Vendrame, 1 R. de Medeiros Person, 1 F. Roche Moreira Latini 1 & L. Castilho 2 1 Technical scientifc department Colsan – Associação Benefcente de Coleta de Sangue, São Paulo, SP, Brazil, and 2 Molecular Immunohematology Laboratory Hemocentro – Unicamp, Campinas, SP, Brazil Received 8 December 2015; accepted for publication 1 April 2016 SUMMARY Background: Te high homology and opposite orientation of RH genes promote rearrangements between them and gener- ate a large number of RHD and RHCE variants which can be inherited together. Searching of RHD-CE genotypes predicting partial antigens in donors is of interest in order to fnd more closely matched donors for African descent patients. Tis study aimed to evaluate a molecular approach to search for RhCE variants in a cohort of individuals with altered expression of D antigen and determine the association of RH variant alleles in Brazilian blood donors. Methods: From 80,961 blood samples tested, 421 with atypical D typing results were studied. Te samples were phenotyped for C, c, E, e antigens. Rh variants were identifed using molecular techniques. Results: All 421 samples had altered RHD alleles, being 56·3% of them partial D. Among them, 94·9% presented variant RHCE*ce and the most common associations were: RHD*weak D type 4.2.2 with RHCE*ceAR; RHD*DAR linked to RHCE*ceVS.02; RHD*weak D type 4.0 linked to RHCE*ceVS.02 and RHCE*ce (c.48C, c.105T, c.733G, c.744C, c.1025T). Among the samples with RhCE variants, 10·6% predict partial c, partial e, hr B - and/or hr S - and 100% express low prevalence antigens. Conclusion: Targeting individuals with altered expression of D antigen can be a good strategy for fnding donors with RhCE variants. In our study 94·9% of the partial D samples revealed altered RHCE variant alleles and 5·7% of the samples with altered RHD allele predicted partial c, partial e and the lack of the high prevalence hr B and hr S antigens. Key words: blood group genotyping, partial RhD, Rh variants, RhCE alleles. Correspondence: Carine Prisco Arnoni, Colsan – Associação Benefcente de Coleta de Sangue, Avenida Jandira 1260, IN, CEP 04080-006, Brazil. Tel.: +55 11 5055 6588; fax: +55 11 5055 6588; e-mail: carine.arnoni@colsan.org.br Rh system is one of the most important and complex blood group systems (Flegel, 2007; Westhof, 2007), which is composed by two homologous genes, RHD and RHCE, encoding the RhD and RhCE proteins. Approximately 50 antigens in addition to the fve major Rh antigens (D, C, E, c and e) are encoded by these genes. Te large number of antigens is attributable to the com- plex genetic basis of RH genes (Flegel, 2007), including the posi- tion on the chromosome and the high similarity between them, that promotes gene rearrangements (Okuda et al., 2000; Suto et al., 2000), besides single nucleotide polymorphisms (SNPs), deletions and insertions which may give rise to a large number of variant RhD and RhCE proteins. Over 200 RHD and 80 RHCE alleles were reported (http:// www.isbtweb.org/working-parties/red-cell-immunogenetics- and-blood-group-terminology/). Altered RH alleles may lead to weak expression, loss of epitopes and expression of new anti- gens. Variant RHD and RHCE alleles are prevalent in individuals of African descent with alleles encoding altered (partial) anti- gens. Patients with partial Rh antigens can make alloantibodies corresponding to the epitopes missing from the altered antigen (Hue-Roye et al., 2011; Noizat-Pirenne & Tournamille, 2011; Westhof et al., 2013b) and these Rh antibodies can be clinically signifcant (Chou et al., 2013; Sippert et al., 2015). Many variant RHCE*ce alleles encoding partial e antigens have been described expressing low-prevalence antigens (e.g. V and VS) and lacking high-prevalence antigens, such as hr B and hr S , contributing to Rh alloimmunization (Noizat-Pirenne & Tournamille, 2011). Terefore, transfusion dependent patients of African origin can make complex antibody specifcities, such as anti-hr S and anti-hr B , and present a challenge with regard to fnding compatible blood for them (Reid et al., 2014). Another level of complexity occurs when the variant RHCE is inherited with an altered RHD. Some combinations are more common than others, e.g. RHCE*ceTI is frequently in cis to RHD*DIVa-2 (Westhof et al., 2013a), RHCE*ceAR or RHCE*ceEK are inherited with RHD*DAR (Hemker et al., 1999), RHCE*ceMO is ofen found with RHD*DAU0 (Westhof et al., 2013b), RHCE*ceBI is linked to RHD*DOL (Roussel et al., 2012) and RHCE*ce48C,733G,1006T is usually associated to RHD*DIIIa (Westhof et al., 2010). © 2016 British Blood Transfusion Society doi: 10.1111/tme.12309