Thymocytes may persist and differentiate without any input from bone marrow progenitors.

Area of Science:

• Immunology
• Developmental Biology
• Transplantation Science

Background:

• Thymus transplants are used for epithelial defects but not T cell-intrinsic deficiencies.
• Existing dogma suggests thymocytes have short lifespans and are replaced by bone marrow progenitors.

Purpose of the Study:

• To investigate the self-renewal capacity of thymocytes in transplanted neonatal thymi.
• To explore the potential of thymus transplantation for correcting T cell-intrinsic deficiencies.

Main Methods:

• Transplantation of neonatal thymi into interleukin 7 receptor-deficient hosts.
• Assessment of thymocyte self-renewal, T cell generation, and peripheral T cell repertoire reconstitution.
• Allogeneic thymus transplantation across major histocompatibility barriers.

Main Results:

• Neonatal thymus transplants in deficient hosts demonstrated extensive self-renewal capacity.
• Continuous thymocyte generation and export were observed, reconstituting diverse peripheral T cell repertoires.
• Allogeneic thymus transplants were not rejected and did not induce graft-versus-host disease, offering protection against infection.

Conclusions:

• Thymocytes possess a greater self-renewal capacity than previously believed.
• Neonatal thymus transplantation is a viable strategy for correcting T cell-intrinsic deficiencies.
• Thymocyte survival depends on competition between incoming progenitors and resident cells.