Non-HLA associations with autoimmune diseases.

Susceptibility to autoimmune diseases (AID) has been associated with multiple combinations of genes and environmental or stochastic factors. The strongest influence on susceptibility to autoimmunity is the major histocompatibility complex (MHC), in particular HLA; however, linkage analyses among multiple affected family members have established that non-MHC chromosomal susceptibility regions also influence the susceptibility towards AID. Besides HLA, three non-HLA genes have been convincingly associated with different AID: Citotoxic T lymphocyte-associated antigen 4 (CTLA4), Protein Tyrosine Phosphatase (PTPN22) and Tumor Necrosis Factor-alpha (TNF), indicating that autoimmune phenotypes could represent pleiotropic outcomes of non-specific diseases' genes that underline similar immunogenetic mechanisms. Identification of genes that generate susceptibility will enhance our understanding of the mechanisms that mediate these complex diseases and will allow us to predict and/or prevent them as well as to discover new therapeutic interventions.