A new HLA-B44 allele (B*44020102S) with a splicing mutation leading to a complete deletion of exon 5.
Using a combination of serology and polymerase chain reaction with sequence-specific primer (PCR-SSP), we have identified in a volunteer bone marrow donor a new HLA class I antigen within the B44 serotype. This human leukocyte antigen (HLA)-B44 variant was typed as 'blank' by microlymphocytotoxicity, whereas the B*44020101 allele was identified by PCR-SSP. A family study confirmed the Mendelian segregation of this blank antigen identified on one of the maternal haplotype transmitted to her child. The DNA sequence of B*44new, now referred to as B*44020102S, performed from the promoter region to the 3' untranslated region revealed a single nucleotide difference (A/G) compared to B*44020101 at the end of intron 4 in the acceptor-splicing site. This mutation leads to an incorrect splicing characterized by the deletion of exon 5 that encodes the transmembrane domain of the HLA antigen. Indeed, full-length complementary DNA sequencing revealed a complete absence of exon 5. Fluorescence-activated cell sorter analysis confirmed the absence of expression of HLA-B44 on the cell surface in the donor, compared to the HLA-B44 positive control. The isoelectric focusing analysis failed to reveal the presence of an HLA-B44 antigen in the donor, showing that no normal HLA-B*44020101 allele was synthesized. The new B*440201010102S allele is a soluble form of B44 without any detectable cell-surface expression. It can thus be considered as a soluble antigen, a form apparently inactive and unfit for antigen presentation.
Dubois
V
V
Histocompatibility Laboratory, EFS Rhône-Alpes, Lyon, France.
Tiercy
J M
JM
Labonne
M P
MP
Dormoy
A
A
Gebuhrer
L
L
D020413:3' Untranslated Regions; D000483:Alleles; D017398:Alternative Splicing; D017951:Antigen Presentation; D001853:Bone Marrow / Q000378:metabolism; D020090:Chromosome Segregation; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics*; D005260:Female; D005434:Flow Cytometry; D017353:Gene Deletion; D014644:Genetic Variation; D015235:HLA-B Antigens / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D059948:HLA-B44 Antigen; D006801:Humans; D007525:Isoelectric Focusing; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics
D020413:3' Untranslated Regions; D018076:DNA, Complementary; D015235:HLA-B Antigens; D059948:HLA-B44 Antigen