T-lymphocyte homeostasis and function in infant baboons: implications for transplantation

Area of Science:

• Immunology
• Comparative immunology
• Transplantation immunology

Background:

• Laboratory mice exhibit neonatal lymphopenia and develop memory T cells, but are prone to immunologic tolerance.
• Understanding infant immune responses in higher animals is crucial for transplantation research.

Purpose of the Study:

• To investigate if fundamental immunologic observations in mice, such as lymphopenia-induced proliferation and tolerance, apply to infant baboons.
• To evaluate the baboon as a model for studying the infant immune system in the context of transplantation.

Main Methods:

• Flow cytometry analysis of peripheral blood cells in infant baboons.
• Assessment of immune responses to artery patch allografts and xenografts.
• Evaluation of immunosuppressive therapies including anti-thymocyte globulin (ATG), anti-CD154 mAb, and mycophenolate mofetil.
• Monitoring of T cell proliferation and mixed lymphocyte reactions.

Main Results:

• Infant baboons are born relatively lymphopenic and expand their naive T cell pool with memory T cells.
• Non-immunosuppressed baboons mounted immune responses against allografts and xenografts.
• Immunosuppression effectively prevented T cell-mediated rejection, and lymphocyte depletion with ATG induced homeostatic T cell proliferation.
• Unlike mice, infant baboons showed no signs of T cell tolerance.

Conclusions:

• The baboon is a suitable model for studying the infant immune system and transplantation immunology.
• Neonatal lymphopenia and memory T cell expansion in baboons do not lead to T cell tolerance, differing from mice.
• The expansion of memory T cells may pose challenges for tapering immunosuppression and achieving long-term immunologic tolerance in baboons.