PTPN22 Trp620 explains the association of chromosome 1p13 with type 1 diabetes and shows a statistical interaction with HLA class II genotypes.
Smyth DJ, Cooper JD, Howson JM, Walker NM, Plagnol V, Stevens H, Clayton DG, Todd JA. Diabetes. 2008 Jun; 57(6):1730-7. Epub 2008 Feb 27.