RHCE-D-CE hybrid genes can cause false-negative DNA typing of the Rh e antigen.

BACKGROUND AND OBJECTIVES: DNA typing of the human Rh blood groups generally shows good agreement with serologically defined phenotypes. However, in the present report we describe four individuals who were declared Rh e negative by genotyping although they express the Rh e antigen.

MATERIALS AND METHODS: Serotyping was performed using mono- and polyclonal Rh antisera. Fluorescent multiplex sequence-specific polymerase chain reactions (PCR-SSPs) identified RHD exons and the polymorphisms usually associated with the Rh E/e or Rh C/c/C(W) antigens. Additional PCR amplification reactions, which were carried out to reveal RHCE-D-CE hybrid genes, analysed exon 5 of the RH genes, the location of the polymorphism (676C-->G) coding for the Rh E and Rh e antigens.

RESULTS: Four individuals were identified who expressed Rh e antigens but were negative by PCR-SSP typing for common Rhe-coding sequences. In one family analysed in detail, an RHCE-D5-CE hybrid gene associated with Rh e antigen expression was identified. A concomitant RHcE allele accounted for a seemingly regular typing pattern by conventional RH PCR.

CONCLUSIONS: The presence of RHCE-D5-CE hybrid alleles may cause false-negative DNA-typing results for the Rh e antigen that are easily overlooked unless appropriate RH hybrid PCR-SSPs are incorporated into conventional DNA-typing protocols. These and previous data strongly caution against an uncritical interpretation of RH DNA-typing results.