Six newly identified HLA-DRB alleles: DRB1*1121, *1419, *1420, *1421, DRB3*0203 and DRB5*0103.

Seven samples with irregular PCR-SSO hybridization patterns, observed during routine HLA-DRB typing, were studied in more detail. Group-specific amplification, followed by hybridization with relevant SSOs strengthened the suggestion that these samples contained new DRB alleles. DRB exon 2 segments were amplified, cloned and sequenced and revealed: DRB11121 [MUL] is similar to DRB11102 in which codon 85 changed from GTT(V) into GTC(A); DRB11419 [AKKAL] is similar to DRB11402 with codon 71 changed from AGG(R) into AAG(K); DRB11420 [OND-52971] is a DRB11406 with codon 37 changed from AAC(N) into TTC(F); DRB11421 [TGI] is similar to DRB11417 with codon 71 changed from AGG(R) into AAG(K); DRB30203 [POS] is similar to DRB30202 in which codons 37-38 are changed from TAC GCG(YA) into TCC GTC(SV); DRB50103 was found in two unrelated individuals of Oriental origin [IND-24 and IND-59] and is similar to DRB50102 in which codon 71 AGG(R) changed into ACG(T). This particular sequence variation at position 71 has not yet been described. The new DRB sequences were confirmed using the sequencing based typing technique. Low resolution PCR-SSP typing failed to amplify two of the DRB114 variants, whereas high resolution PCR-SSP resulted in aberrant patterns. Class II alloantisera identify the codon 71 changes in DRB11419 and *1421 with respect to the MC1 ('DR1+DR4') epitope.