NOD2 and Crohn disease: For example, rare (MAF <3%) protective IFIH1 mutations against type 1 diabetes (T1D) suggest a causative factor may be a host response to an enterovirus [20], whereas cytokine secretion by peripheral mononuclear cells has been recognised as being important in the pathogenesis of Crohn’s disease, in part through its defect in the context of NOD2 mutations [21].