To investigate whether the presence of the C1858T PTPN22 variant in T1D patients altered the ability of neutrophils to be recruited to the pancreas, potentially leading to insulitis, the behavior (adhesion and transmigration) of neutrophils isolated from the wild-type (C1858C) and heterozygous (C1858T) T1D patients on endothelial cell monolayers stimulated with TNF-α was examined. Here, PTPN22 is linked to type 1 diabetes mellitus.