Absence of association of TAP and LMP genes with type 1 (insulin-dependent) diabetes mellitus.

Although one of the major genes which cause type 1 (insulin-dependent) diabetes mellitus is located in the class II HLA region in humans, its precise location is still unknown. In order to investigate whether TAP (Transporter associated with Antigen Processing) and LMP (Low Molecular Weight Polypeptide) genes, which are located in the class II HLA region, are HLA-linked diabetogenic genes, the association of TAP1, TAP2 and LMP2 genes with type 1 diabetes was analyzed in the Japanese population. No difference in allele frequencies of these genes was detected between diabetic patients and control subjects. On the other hand, DQA1 and DQB1 genes showed significant association with type 1 diabetes. These data suggest that the diabetogenic gene in the class II HLA region may be located near the DQA1 and DQB1 loci, rather than the TAP and LMP loci.