Sublethal Total Body Irradiation Causes Long-Term Deficits in Thymus Function by Reducing Lymphoid Progenitors

Area of Science:

• Immunology
• Radiation Biology
• Hematopoiesis

Background:

• Total body irradiation (TBI) affects hematopoietic cells, but long-term consequences on thymopoiesis with aging are not fully understood.
• Understanding radiation's impact on the immune system is crucial for managing TBI events and developing therapies.

Purpose of the Study:

• To investigate the long-term effects of single-dose irradiation on thymopoiesis and hematopoietic stem cells (HSCs) in mice.
• To determine sex-specific differences in radiation-induced thymic damage and aging.

Main Methods:

• Mice were exposed to varying doses of TBI.
• Thymopoiesis, progenitor cell populations (cKit+), HSCs, and thymic epithelial cells were analyzed over time.
• T lineage commitment potential and gene expression (Ccl25) were assessed.

Main Results:

• A single TBI dose caused long-term, dose-dependent suppression of thymopoiesis (≥12 months) in both sexes.
• Radiation significantly reduced thymic lymphoid progenitors and bone marrow HSCs, with greater impact in females.
• Aging-associated thymic involution was accelerated, and T lineage commitment potential was reduced.

Conclusions:

• Sublethal TBI can cause permanent damage to HSCs and T cell production capacity, accelerating thymic aging.
• Reduced progenitor numbers and impaired T lineage commitment contribute to long-term thymopoiesis suppression.
• Findings have implications for evaluating and treating TBI in humans.