The most important issue for us is to understand the annotation system of HLA allele and its relation to HLA antigen (HLA type). HLA alleles express as co-dominant genetic traits and it is well known that the gene frequency of HLA alleles is varied among human races and ethnic groups, due to the presence of extensive polymorphisms in the genes for HLA. In addition, there are strong linkage disequilibria among alleles of different HLA genes, forming HLA haplotypes, which is also characteristic to race or ethnic groups. Moreover, previous studies have repeatedly reported that there are associations of specific HLA antigen or alleles with the susceptibility or resistance to several autoimmune diseases and chronic inflammatory diseases.