The RHCE allele ceRT: D epitope 6 expression does not require D-specific amino acids.
BACKGROUND
False-positive D typing in patients may lead to anti-D immunization caused by D+ transfusions or by omission of anti-D prophylaxis. Known causes of such errors are RhCE variants carrying RhD-specific amino acids and cold agglutinin activity of some frequently used monoclonal anti-D.


METHODS
The molecular basis of eight samples referred because of "false-positive" reactions with some commercial monoclonal anti-D was investigated by PCR and nucleotide sequencing from genomic DNA. PCR with sequence-specific priming was developed to specifically detect the underlying aberrant RHCE allele. The D epitope profile of the allele was determined by serology.


RESULTS
The aberrant reactivity of the samples was caused by the RHCE allele RHCE(R154T) that occurred in a cde haplotype. The phenotype dubbed ceRT expressed the important D epitope 6, which is the target epitope of most monoclonal anti-D used in routine typing.


CONCLUSIONS
The characterization of ceRT demonstrated a previously unknown mechanism of antigen D expression that does not require any D-specific amino acid. At least for some D epitopes, D-like structures may be mimicked by RhCE proteins carrying amino acid substitutions not representative for RhD.
Wagner
Franz F
FF
Department of Transfusion Medicine, University of Ulm, Ulm, Germany.
Ladewig
Birgit
B
Flegel
Willy A
WA
D000123:Acetyltransferases; D000372:Agglutination Tests; D000483:Alleles; D000595:Amino Acid Sequence; D051046:Amino-Acid N-Acetyltransferase; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D001788:Blood Grouping and Crossmatching / Q000592:standards; D000939:Epitopes / Q000097:blood* / Q000235:genetics / Q000276:immunology; D005189:False Positive Reactions; D005838:Genotype; D006023:Glycoproteins / Q000235:genetics* / Q000276:immunology; D006801:Humans; D010641:Phenotype; D015995:Prevalence; D012204:Rh-Hr Blood-Group System / Q000235:genetics* / Q000276:immunology
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006023:Glycoproteins; C066468:RHCE protein, human; D012204:Rh-Hr Blood-Group System; D000123:Acetyltransferases; D051046:Amino-Acid N-Acetyltransferase; C494874:NAGS protein, human