Human interleukin-2 receptor beta mutations associated with defects in immunity and peripheral tolerance

Abstract Interleukin-2, which conveys essential signals for effective immunity and immunological tolerance, operates through a heterotrimeric receptor. Genetic deficiency of the alpha or gamma chain causes debilitating disease. Here we identify human interleukin-2 receptor (IL-2R) beta chain (IL2RB) gene defects as a cause of life-threatening immune dysregulation. We report three homozygous mutations in the human IL2RB gene of eight individuals from four consanguineous families that cause disease by distinct mechanisms. Nearly all patients presented with autoantibodies, hypergammaglobulinemia, bowel inflammation, dermatological abnormalities, and cytomegalovirus disease. Patient T lymphocytes lacked surface expression of IL-2Rbeta and were unable to respond normally to high-dose IL-2 stimulation. By contrast, patient natural killer (NK) cells retained partial IL-2Rbeta expression and cytotoxic function. IL-2Rbeta loss of function was recapitulated in a recombinant system, in which endoplasmic reticulum sequestration was revealed as the mechanism by which certain missense mutations cause disease. Hematopoietic stem cell transplant resulted in resolution of clinical symptoms in one patient. The hypomorphic nature of this disease highlights the significance of variable IL-2Rbeta expression between different lymphocyte subsets and during their maturation as a means of modulating immune function. Insights from these patients can inform the development of IL-2-based therapeutics for immunological diseases and cancer.