Before the April 2010 HLA nomenclature update, new HLA-DPB1 allele names were assigned within the existing nomenclature system. For example, the allele discovered after HLA-DPB1*9901 was assigned as DPB1*0102, the subsequent allele was named DPB1*0202, then *0302 and so on. This name assignment was decided because of the complex genetic characteristics of DPB1 alleles compared to alleles of other HLA loci. The majority of the HLA-DPB1 alleles cannot be simply grouped together by their nucleotide sequences. This name assignment has been the most confusing system within the HLA nomenclature. In the 2010 HLA nomenclature update, all DPB1 alleles, except DPB1*0202 and *0402, discovered after DPB1*9901 were reassigned with new numbers. For example, DPB1*0102 becomes DPB1*100:01