CD4 and immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome: CD4+ T cells are thought to be at least partially responsible for AIE based on (a) the phenotypic similarities between AIE and the IPEX syndrome [21,22], (b) the role of CD4+ T cells in villous atrophy [23] and (c) the aberrant CD4+ T cell subsets and CD4+ IEL reported in some cases of AIE [5].