HLA Class I or Class II and Disease Association: Catch the Difference if You Can

The association of autoimmune diseases with HLA has been known for many decades. To date, however, the underlying mechanisms have not been fully understood. The recently introduced genome-wide association studies (GWAS) have suggested that several genes converging in common pathways contribute to the genetic susceptibility in such disorders. Nevertheless, for most autoimmune/autoinflammatory diseases, the HLA genes are by far the strongest risk factors. The basis of some associations has now been elucidated, particularly in those cases in which exogenous factors are involved.