Interestingly, all autoimmune diseases reported to be associated with the PTPN22-1858T allele are characterized by the production of autoantibodies [12-14,16,22], suggesting that the 620W variant of LYP could be implicated not only in T-cell activity regulation, but also in B-cell autoreactivity [24]. This evidence concerns the gene PTPN22 and autoimmune disease.