Toward minimal conditioning protocols for allogeneic chimerism in tolerance resistant recipients

Area of Science:

• Immunology
• Transplantation Biology

Background:

• Mixed chimerism is a strategy to achieve donor-specific immunological tolerance.
• Current protocols for chimerism induction can be toxic, necessitating the development of non-myeloablative, minimal intensity approaches.
• The non-obese diabetic (NOD) mouse model presents challenges for inducing chimerism due to resistance from pre-existing T cells.

Purpose of the Study:

• To develop a minimalistic protocol for inducing fully allogeneic mixed chimerism in the NOD mouse model.
• To identify strategies for overcoming T cell resistance to chimerism induction.
• To refine protocols for clinical applicability in achieving immune tolerance.

Main Methods:

• Identification of pre-existing T cells as a barrier to chimerism in NOD mice.
• Utilized monoclonal antibodies targeting NOD T cells to facilitate chimerism.
• Investigated the use of cyclophosphamide as a replacement for anti-CD40 ligand in the conditioning regimen.

Main Results:

• Demonstrated that targeting NOD T cells with monoclonals can establish long-term chimerism and tolerance to donor islets.
• Showed initial success in generating fully allogeneic mixed chimerism in NOD mice by incorporating cyclophosphamide into the conditioning regimen.
• Successfully replaced the clinically inapplicable anti-CD40 ligand with cyclophosphamide, moving towards a more clinically relevant protocol.

Conclusions:

• Pre-existing T cells are a key obstacle to achieving mixed chimerism in the NOD mouse model.
• Targeting T cells and employing cyclophosphamide offers a promising, less toxic strategy for inducing mixed chimerism and immune tolerance.
• This refined protocol represents a significant step towards clinical utility for mixed chimerism induction.