Thymus transplant in the spleen restores aging immunity

The thymus plays a crucial role in the immune system. This is where T cells, the white blood cells that recognize foreign threats, mature and develop. With age, the thymus shrinks and loses function, a process called thymic involution. This partly explains why older people respond less well to infections and vaccines.

Chinese researchers describe in the journal Advanced Science a new approach: growing thymus grafts inside the spleen of mice. The researchers chose the spleen because it has a rich blood supply, secretes growth signals, and is immune-tolerant. That last property makes it better suited for donor (allogeneic) tissue than other implantation sites.

Faster and larger growth than in muscle

The grafts grew faster in the spleen than in muscle tissue, the site currently used clinically in children born without a thymus. Within two weeks, splenic grafts already showed distinct cortical and medullary zones, the two compartments that support different stages of T cell development. Muscle grafts were smaller and partly necrotic.

After transplantation, the mice showed improved immune responses against viruses and tumors. New T cell production increased. The researchers also found that age-related thymic involution was reversed in recipient animals. These are preliminary results in mouse models, and the step to humans is large, but the findings are promising.

Broader context

Thymic involution is one of the best-documented features of immune aging. Efforts to regenerate the thymus via stem cells, growth factors, or thymic preparations are underway globally. The spleen-based approach is novel and may offer a faster and more effective alternative. Whether this works in humans, and how long such a transplant remains functional, remains unknown. Follow-up research in larger animal models is the logical next step.

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