Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is another well-known example, as this locus confers the third highest genetic association for T1D and is also known to be a regulator of signaling in a variety of immune cell types including lymphocytes, monocytes, dendritic cells (DCs), and neutrophils (57). This evidence concerns the gene PTPN22 and type 1 diabetes mellitus.