HLA-DRB1 and autoimmune disease: The HLA genes involved in the immune response are divided into two classes, including class I HLA-A, -B, and-C and class II HLA-DRB1, -DQB1, and -DPB1, which are different in structure and function [9, 10], although genetic studies have found a strong association between HLA-DRB1 gene polymorphism and autoimmune diseases [11].