Within the major histocompatibility locus (MHC) on 6p, many SNPs have been found to be associated with complex diseases such as celiac disease, inflammatory bowel disease, psoriasis, rheumatoid arthritis, diabetes mellitus, schizophrenia, lung cancer and follicular lymphoma [2]–[10]. An analysis of the Catalog of Published Genome-Wide Association Studies [1] revealed that out of 1,167 unique SNP associations with a reported p<5×10−7, 82 (7.0%) were located within the MHC (Fisher's Exact p<10−30). Except for celiac disease [11] it remains largely unclear how MHC variants increase disease susceptibility.
