Molecular structures identified in serologically D- samples of an admixed population.

Background: The D- phenotype is mainly caused by the complete deletion of the RHD gene in Caucasians. However, a plethora of allelic variants have been described among D- individuals from different ethnic groups.

Study Design And Methods: A cohort of 1314 routine serologically D- samples from white Argentineans was studied by molecular methods.

Results: Among the 1314 D- samples, 2.1% showed RHD-specific amplifications. One hybrid Rhesus box was detected in all D-/RHD+ samples, suggesting a hemizygous status. The RHDΨ was found in 0.7% of rr samples while DEL and null variants were detected in 16.7% of the D- samples expressing C and/or E antigens. The variants associated with the C antigen were seven RHD-CE-D(s) , two RHD(1-2)-CE(2-9)-D(10), two previously unreported RHD(329T>C)-CE(3-9)-D null alleles, one RHD(M295I), and one new RHCE(1-2)-RHD(3361del11 -10) null allele whereas those associated with the E antigen were five RHD(46T>C) and one novel RHD(581insG) null allele responsible for a premature stop codon.

Conclusions: The prevalence of D-/RHD+ samples is higher than that observed in Europeans. More than 50% of the RHD alleles found were represented by RHDψ and RHD-CE-D(s) showing the African contribution to the genetic pool of the admixed population analyzed. Interestingly, three new alleles were found, two of them being hybrid structures between previously described RHD variants recombined with RHCE sequences. The knowledge of the RHD allele repertoire in our population allowed the implementation of reliable typing and transfusion strategies for a better management of patients and pregnant women.