A SECOND HLA-B NULL ALLELE: B*5111N.
R Blasczyk1, V. Rebmann2 and H. Grosse-Wilde2.
1Department of Hematology and Oncology, Blood Bank, Charité,
Campus Virchow-Klinikum, Humboldt-University Berlin; 2Institute
of Immunology, University Hospital Essen, Germany.
Several HLA class I null alleles have been described so
far from which only a single one is a HLA-B allele (B*1526N). In
a Caucasian family we have identified by serology a second HLA-B blank
which segregated with one of the father's haplotype. PCR-SSP revealed
an allele belonging to the HLA-B*51 group. PCR-based HLA and biochemical
complement analysis yielded the haplotype A*02 B*51 Bf S C4A 3/13 C4B 1
DRB1*04 DQB1*03. Sequencing based typing of the 2nd and 3rd exon
after haplotype-specific amplification from genomic DNA gave a normal B*5101
sequence. We have then sequenced haplotype-specific and from genomic
DNA a 500 bp fragment of the 3' end of the 5' flanking and untranslated
region, the 1st exon, the 1st, 2nd and 3rd intron and the 4th exon.
Here at the 5' end of exon 4 we have found a C insertion in codon 185,
the first codon of exon 4, which changes the frame of translation and provokes
a stop-codon further downstream in exon 4 inducing chain termination at
codon 196. Thus, the cause of inactivation of B*5111N is identical
with that of A*0104N and 2411N. The nucleotide insertion distinguishing
A*0104N from A*0101, A*2411N from A*2402 and B*5111N from B*5101 is also
present in the pseudogene HLA-J. Since this nucleotide insertion
is not unique and since conversions rather than point mutations are the
common mechanisms for evolving new HLA alleles, it is likely that HLA-J
has served as a donor allele to generate HLA-A*0104N, A*2411N and B*5111N.
In view of transplantation one should be aware that in PCR-based typing
and matching approaches which do not consider the complete gene sequence,
at least the expression of A1, A2, A3, A24, B15 and B51 should be confirmed
by means of serology in order to avoid fatal mismatches.