The highincidence of T1D in Sardinians is due to boththe high frequency of another susceptible haplotype(DRB1*03:01-DQA1*05:01-DQB1*02:01),and the low frequency of protective haplotype(DRB1*15:01-DQA1*01:02-DQB1*06:02) (18).In Japanese population, the absence of the DR3 allelescorrelates with the low incidence of T1D. This evidence concerns the gene HLA-DRB1 and type 1 diabetes mellitus.