Graft-specific immune cells communicate inflammatory immune responses after brain death.

Background: Donor brain death (BD) triggers inflammatory graft activation that leads to impaired graft quality and outcome. We used a mouse BD model to investigate graft inflammation in cardiac transplants from immune-competent and immune-deficient donor animals. Effects of donor T-cell depletion were tested in an additional group of cardiac transplant recipients.

Methods: We analyzed systemic and graft-specific inflammatory activation after BD in donors and in syngeneic recipients of hearts retrieved from BD donors. To dissect the role of donor-specific immune cells in communicating BD-triggered inflammation, immune-deficient T-cell-, B-cell-, and natural killer cell-deficient Rag2/double knockout mice and naïve C57BL6 treated with anti-thymocyte globulin (Thymoglobulin; Genzyme Transplant, Cambridge, MA) were observed.

Results: Donor BD boosted lymphocyte activation in donors and recipients of syngeneic BD grafts. Lymphocyte activation was mitigated in recipients of immune-deficient and Thymoglobulin-treated BD donor grafts. Likewise, systemic and intra-graft levels of inflammatory cytokines interleukin -1, interleukin-6, interferon-γ, and tumor necrosis factor-α were significantly reduced in immune-deficient and anti-thymocyte globulin-treated recipients. Dense lymphocyte infiltrates were detected in the hearts from untreated BD donors; in contrast, the hearts from donors treated with Thymoglobulin demonstrated a preserved structure with minimal infiltrates comparable with naïve controls.

Conclusion: BD triggers inflammatory graft activation communicated through intra-graft immune cells. Donor treatment with Thymoglobulin prevented inflammatory immune activation and improved graft quality to levels comparable to living donor organs.