Figure 1: Illustration of the expression of HLA DQ 2 in cis and trans forms: In cis form, α and β chains of DQ2 are expressed by HLA DQA1*0501 and HLA DQB1*0201 alleles of DR3 haplotype respectively. Whereas in case of trans form, HLA DQA1*0501 allele of DR5 haplotype encodes α chain and DR7 haplotype with DQB1*0202 allele on other chromosome encodes β chain. Then these two chains unite to form HLA DQ2 molecule on Antigen Presenting Cells.