FOXP3 expression following bone marrow transplantation for IPEX syndrome after reduced-intensity conditioning

Area of Science:

• Immunology
• Pediatric Hematology
• Transplantation Medicine

Background:

• IPEX syndrome is a severe X-linked primary immunodeficiency characterized by a FOXP3 gene mutation, leading to absent regulatory T cells and multi-organ autoimmunity.
• Clinical manifestations include eczema, colitis, failure to thrive, and elevated IgE, often requiring intensive management.
• Allogeneic hematopoietic stem cell transplant (HSCT) is a potential curative therapy, but the dynamics of immune reconstitution and correlation with clinical outcomes require further elucidation.

Observation:

• An infant with IPEX syndrome and absent FOXP3 expression underwent reduced-intensity conditioning allogeneic HSCT.
• Post-transplant, rapid engraftment and full donor chimerism were achieved.
• FOXP3 protein expression in CD4+ T cells increased significantly post-HSCT, confirmed by mRNA analysis.

Findings:

• FOXP3+ T regulatory cell reconstitution occurred rapidly after HSCT, correlating with full donor chimerism.
• Increased FOXP3 expression paralleled the resolution of severe clinical symptoms, including eczema, colitis, and feeding intolerance.
• Serum IgE levels dramatically decreased post-transplant, indicating successful immune modulation.

Implications:

• This case provides direct evidence that HSCT is a curative treatment for IPEX syndrome.
• Successful immune reconstitution of FOXP3+ T regulatory cells is a key indicator of therapeutic success post-HSCT.
• The findings support the use of reduced-intensity conditioning regimens in pediatric HSCT for primary immunodeficiencies.