The Rh system is genetically controlled by two different but highly homologous genes on chromosome 1p34-36. The RHCE gene encodes a different RhCcEe polypeptide and the RHD gene encodes the D polypeptide, and there are a large number of antigenic polymorphisms between these two peptides. Of these, the RhDel is characterized as RhD by using a conventional serological test, but it does show absorption and elution of anti-D.1 The molecular basis of RhDel is not known. The blood of 21 Del (21.6%) of 102 serological RHD patients was obtained after an absorption and elution test. A modified polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method based on the polymorphisms between RHCE and RHD genes was used to analyze the Del gene structure,2 and the results showed that there was no difference between the RhD and RhDel gene except that at the BspHI site of exon 9, the Del gene lacked the BspHI site that was similar with the RHCE gene. Haplotyping by Sph I bands showed no gross difference between RHD and RHDel genes3 (data not shown).
