CD4 and polyendocrinopathy: Absent IL2RA signalling causes an immune dysregulation, polyendocrinopathy, enteropathy, and X-linked [IPEX]-like condition due to impaired persistence and function of regulatory T cells.49 Joosse et al. 43 showed that the duplication increases IL2 responsiveness in activated CD4 + T cells, which they postulated could then overstimulate these cells in the antigen-rich environment of the colon and induce inflammation.