CONTRIBUTION OF THE ABSENCE OF ASPARTIC-ACID AT POSITION-57 OF THE HLA-DQ BETA-CHAIN TO PREDISPOSITION TO INSULIN-DEPENDENT DIABETES-MELLITUS IN A SOUTHERN CHINESE POPULATION

Objective To investigate the association of the absence or presence of aspartic acid at position 57 of the HLA-DQ beta chain (NA or A) with susceptibility or resistance to insulin-dependent diabetes mellitus (I DDM) in a Southern Chinese population. Methods Sixty-nine IDDM patient s and 47 healthy controls in a Southern Chinese population were HLA-DQ B1 genotyped by one-step sequence specific polymerase chain reaction ( ssPCR). Results The frequencies of NA and A were 64.5% and 35.5% in th e IDDM patients, and 40.4% and 59.6% in the control subjects respectiv ely (RR for NA was 2.68, P< 0.01). The frequencies of NA/NA, NA/A and A/A phenotypes were 47.8%, 33.3% and 18.8% in the IDDM patients, and 3 1.9%, 17.0% and 51.1% in the controls respectively (P< 0.01). The freq uency of A/A phenotype was significantly lower in the IDDM patients th an in the control subjects (RR = 0.22, P < 0.01). DQB1 0302 and DQS1* 0201 were more frequent in IDDM patients than in control subjects. Th e younger the age of IDDM onset, the higher the allele frequencies of DQB1 0201 and DQB1* 0302. Conclusion The present study suggests that the NA confers the susceptibility to IDDM, while the A confers the pro tection against IDDM in patients of Southern Chinese origin. These ass ociations are more clearcut in childhood-onset IDDM patients.