Application of induced pluripotent stem cells to primary immunodeficiency diseases.

Primary immunodeficiency diseases (PIDs) are a heterogeneous group of rare immune disorders with genetic causes. Effective treatments using hematopoietic stem cells or pharmaceutical agents have been around for decades. However, for many patients, these treatment options are ineffective, partly because the rarity of these PIDs complicates the diagnosis and therapy. Induced pluripotent stem cells (iPSCs) offer a potential solution to these problems. The proliferative capacity of iPSCs allows for the preparation of a large, stable supply of hematopoietic cells with the same genome as the patient, allowing for new human cell models that can trace cellular abnormalities during the pathogenesis and lead to new drug discovery. PID models using patient iPSCs have been instrumental in identifying deviations in the development or function of several types of immune cells, revealing new molecular targets for experimental therapies. These models are only in their early stages and for the most part have recapitulated results from existing models using animals or primary cells. However, iPSC-based models are being used to study complex diseases of other organs, including those with multigenic causes, suggesting that advances in differentiation processes will expand iPSC-based models to complex PIDs as well.