[Common genetic factors in autoimmunity]

Autoimmune diseases (AIDs), including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) among others, are characterized by a complex etiology in which the combination of several genetic and environmental factors leads to an altered immune response. Several lines of evidence, such as the presence of chromosomal regions associated with several AIDs and the existence of similar gene expression patterns in autoimmune disorders, suggest that different AIDs share common genetic factors. The identification of common genetic factors associated with autoimmunity is of great relevance, since it will allow a better understanding of disease pathogenesis and could help for the development of molecular diagnosis tools and new therapeutic targets. In the past few years, a great progress has been made in the knowledge of the common genetic factors associated with autoimmunity. The PTPN22 gene, an important regulator of T cell response, has been identified as a relevant genetic marker for AIDs. This gene is implicated in the susceptibility to autoimmune disorders such as, RA, SLE, and type 1 diabetes (T1D). In the case of RA the association with the PTPN22 gene is the most replicated after association with HLA genes. In addition, genes implicated in the altered balance between cytokines, such as MIF and IRF5, have been identified as genetic factors predisposing to AIDs.