TAP2 genes are placed within the HLA complex, have limited genetic variability and encode two main groups of peptide transporter proteins, the so-called TAP2*01 alleles, with a short ATP-binding domain, and the TAP2*0201 allele with a long domain. These transporters carry antigenic peptides from cytoplasm across the endoplasmic reticulum membrane to release them into nascent HLA class I molecules, which will then travel towards the plasma membrane. The shorter TAP2*01 alleles are present in 99% of diabetics and 90% of controls; these alleles may add slight, although significant and independent, susceptibility to diabetes, particularly in subjects carrying non-Asp 57 at beta DQ. Moreover, this increased susceptibility is not due to linkage disequilibrium with other HLA markers (i.e.: DR4), which does not exist in our Spanish population.