The indirect alloimmune response causes microvascular endothelial dysfunction-a possible role for alloantibody

Area of Science:

• Immunology
• Cardiology
• Transplantation Science

Background:

• Endothelial dysfunction post-cardiac transplantation lacks clear causative agents.
• This study investigates the indirect alloimmune response's role in endothelial dysfunction using a major histocompatibility complex class I mismatch model.

Purpose of the Study:

• To determine if the indirect alloimmune response mediates endothelial dysfunction after cardiac transplantation.
• To elucidate the mechanisms underlying graft vasculopathy and impaired endothelial function.

Main Methods:

• Rat cardiac transplantation model (PVG.RT1 hearts into PVG.R8 recipients).
• Assessment of alloantibody, cardiac allograft vasculopathy, inflammatory infiltrate, and endothelial cell origin.
• Evaluation of endothelial function using Langendorff preparations.

Main Results:

• Allografts showed significant luminal occlusion and inflammatory infiltrates (CD11b monocytes, CD4 T cells, C4d deposition).
• Both syngeneic and allogeneic grafts exhibited transient endothelial dysfunction, with allografts showing persistent impairment in basal coronary flow and vasodilator response.
• Antibody against major histocompatibility complex class I inhibited endothelium-dependent vasodilation.

Conclusions:

• Transient microvascular endothelial dysfunction occurs in both syngeneic and allogeneic cardiac grafts.
• Allogeneic grafts fail to recover, indicating the indirect immune response (CD4 T cells, monocytes, antibody) mediates endothelial dysfunction.
• Alloantibody likely plays a significant role in the development of endothelial dysfunction post-transplant.