[Analysis of TAP gene in IDDM]

Abstract

Transporter associated with antigen processing (TAP) is a molecule required for endogenous antigen processing and is encoded in MHC class II region. We have typed TAP polymorphism in 95 patients with insulin-dependent diabetes mellitus (IDDM) and 75 normal controls. TAP alleles were typed by PCR-SSO method. There was no significant difference between IDDM patients and normal controls in the frequencies of TAP 1 and TAP 2 alleles. On the contrary, HLA-DQ locus showed strong association with IDDM in the same series of subjects. Positive linkage disequilibrium was observed between HLA-DQB1*0303 and TAP 2C, and HLA-DQB1*0401 and TAP 2B. Negative linkage disequilibrium was observed between HLA-DQA1*0103 and TAP 2A. We conclude that it is not TAP but HLA-DQ that exhibits primary association with IDDM.