UNDEFINABLE TYPING RESULTS REVEAL A NEW DRB1*08 ALLELE (DRB1*0820).
Mersch Guy1, Vandekerckhove Bart2, Lebeer
Katleen1, Van Hulle Hilde2, Van Reybroeck Georges1,
Rossau Rudi1. 1Innogenetics N.V., Gent;
2BTC Oost-Vlaanderen Laboratorium Immunohematologie, Gent.
A routine sample from the "Laboratorium Immunohematologie
BTC Oost-Vlaanderen" was typed for the DR locus with Dynal-SSP and INNO-LiPA
DRB key DRB1+3+4+5. From the SSP results, it was clear that a DR4 and a
DR53 were present. The second DR locus however couldn't be determined due
to an unusual combination of positive reactions. Also the INNO-LiPA resulted
in "No combinations found!". Therefore this sample was sent to Innogenetics
for further investigation. According to the aberrant probe pattern on the
LiPA DRB decoder (second generation) we presumed the presence of a new
allele which was very similar to DRB1*08041 except for one probe reaction
(probe 8). Another probe (probe 9) for a sequence in the same, first hyper
variable region of the DRB exon 2 locus showed a positive reaction. To
reveal the correct sequence, this allele was cloned into a pGEMT-vector
(Promega) and the nucleotide sequence analysis was performed using an automated
sequencer Model 373A (Applied Biosystems) with fluorescence-labelled dideoxy
nucleotide terminators. The obtained sequence was concordant with the previous
results. These results were sent to the WHO Nomenclature Committee for
factors of the HLA System and this new allele was assigned as DRB1*0820.
Comparing this new DRB1*08-allele to the other 22 DRB1*08-alleles described
so far, only this DRB1*08-allele has another pattern in the first hyper
variable region of exon 2. Because of the existence of this sequence pattern
in other DRB-alleles, it is possible that this allele was created by a
crossing over event.