PTPN22 and viral infectious disease: The rs2476601 SNP within PTPN22 has been associated with lower IFN production by macrophages in response to TLR ligand stimulation (as would occur during viral infection) [94], and additionally it has been suggested that PTPN22 could suppress the function of effector T cells, diminishing their response to viral infection and allowing the establishment of persistent infection [91,95].