RHD*DOL1 and RHD*DOL2 encode a partial D antigen and are in cis with the rare RHCE*ceBI allele in people of African descent.

BACKGROUND

Several studies showed in people of African descent the existence of a genetic linkage between RHD alleles encoding a variant D antigen and a given altered RHCEce allele. RHCEceBI is a rare allele encountered in people of African descent, that encodes a Hr- hr(S) - Rhce protein. Our study shows that RHCEceBI appears to be genetically linked to two very similar variant RHD alleles, RHDDOL1 and RHD*DOL2, and demonstrates for the first time that DOL-2 is a partial D antigen.

STUDY DESIGN AND METHODS

After finding out an individual with both RHCEceBI and RHDDOL presumed to be in cis, we hypothesized a genetic linkage between those two genes. All individuals (n = 7) known to carry RHCE*ceBI in our laboratory, including the index case, were fully investigated at the serologic and molecular level.

RESULTS

One individual with alloanti-D, being homozygous for RHCEceBI and RHDDOL2, allowed us to confirm the genetic linkage between those two genes, as well as the partial D status of DOL-2. In the six RHCEceBI remaining individuals, three were found with RHDDOL2 and 3 with RHD*DOL1, likely in cis. Three of them made an alloanti-D; one was DOL-1 and two were DOL-2.

CONCLUSION

The rare RHCEceBI allele appears to be in cis either with RHDDOL1 or with RHDDOL2 in people of African descent. DOL-1 and DOL-2 must be considered as partial D antigens. We recommend a systematic search for RHDDOL1 and RHDDOL2 in people found to carry RHCEceBI and vice versa, especially in patients with sickle cell disease.