DQ5 β-chains combine with α-chains, encoded by genetically linked HLA-DQA1 alleles, to form the cis-haplotype isoforms.

Compared to DQ2 serotyping of DQB1*0201 positive individuals (98%), the efficiency of DQ5 recognition is relatively low and error prone.

While DQ5 recognizes DQB1*05 alleles more efficiently than DQ1, the serotyping is rather poor method of typing for transplantation or disease association prediction or study.

DQ5 is negatively associated with (protective against) idiopathic nephrotic syndrome in Polish children,[2] and adrenocortical failure (Addison's disease).

[7] DQ5 is shown to be associated with increased risk of gastric mucosal atrophy in Helicobacter pylori infected subjects.