RHD and RHCE molecular analysis in weak D blood donors and in patients with Rh antibodies against their own corresponding Rh antigen

Background - The Rh system is the largest and most polymorphic blood group system. The existence of a large number of RH alleles results in variant phenotypes that often complicate blood donor phenotyping and the distinction between auto- and alto-antibodies in recipients who have anti-Rh antibodies in the presence of their own corresponding Rh antigen. Knowledge of these variants is necessary in order to make blood transfusion safer. Materials and methods - Samples from 48 blood donors with serological weak D and from 29 patients who had anti-Rh antibody in the presence of their own corresponding Rh antigen were evaluated molecularly for RHD and RHCE alleles using a blood-multiplex ligation-dependent probe amplification assay and Sanger sequencing. Results - Rh variants were found in 45 of the 48 blood donors: 24/45 (53%) were weak D, 2/45 (4%) partial D and 19/45 (42%) were weak and partial D. The remaining three donors (6%) did not show a mutation in the RHD allele. Among the 29 patients, 13/29 had anti-e, of whom 4/13 had genotypes that predicted a partial e antigen; 11/29 had anti-D, with 6/11 being identified as partial D; 2/29 had anti-c, of whom 1/2 was predicted to express partial c antigen; 4/29 who had anti-E and 4/29 who had anti-C did not show mutations in RHCE*C or RHCE*E. Discussion - It was possible to find individuals with clinically significant Rh phenotypes due to the weak reactivity of the D antigen, detected through serological tests in blood donors. In patients, when found with the anti-Rh antibody in the presence of the same Rh antigen, it is difficult to distinguish an auto-antibody from an alto-antibody by serological tests; in these cases, molecular methods (genotyping) can help us to determine whether there are changes in the RH alleles and to discover the nature of the antibody (alto or auto).