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

Area of Science:

• Immunology
• Genetics
• Molecular Biology

Background:

• Interleukin-2 (IL-2) is crucial for immune responses, signaling through a heterotrimeric receptor.
• Defects in immune system components can lead to severe immune dysregulation and life-threatening conditions.

Purpose of the Study:

• To identify the genetic cause of severe immune dysregulation in affected individuals.
• To elucidate the molecular mechanisms by which IL2RB mutations lead to disease.
• To explore potential therapeutic strategies for IL-2 receptor-related immunodeficiencies.

Main Methods:

• Genetic sequencing to identify mutations in the IL2RB gene.
• Flow cytometry to assess IL-2 receptor beta chain (IL-2Rβ) surface expression on patient immune cells.
• Functional assays to evaluate T cell and natural killer (NK) cell responses to IL-2 stimulation.
• Recombinant protein studies to confirm the impact of mutations on IL-2Rβ function.

Main Results:

• Identified three homozygous IL2RB mutations in eight individuals from four families presenting with severe immune dysregulation.
• Patients exhibited autoantibodies, hypergammaglobulinemia, inflammation, and susceptibility to infections like cytomegalovirus disease.
• Patient T lymphocytes showed absent IL-2Rβ surface expression and non-responsiveness to IL-2, while NK cells retained partial function.
• In vitro studies confirmed that IL2RB mutations reduce IL-2Rβ surface expression and IL-2 binding.

Conclusions:

• Germline mutations in the IL2RB gene are a cause of severe, life-threatening immune dysregulation.
• Understanding the functional consequences of IL-2Rβ defects provides insights into IL-2 signaling pathways.
• Stem cell transplantation and gene therapy approaches show promise for treating IL-2Rβ deficiency disorders.