Antibody-Mediated Rejection in Sensitized Nonhuman Primates: Modeling Human Biology

We have established a model of sensitization in nonhuman primates and tested two immunosuppressive regimens. Animals underwent fully mismatched skin transplantation, and donor-specific antibody (DSA) response was monitored by flow cross-match. Sensitized animals subsequently underwent kidney transplantation from their skin donor. Immunosuppression included tacrolimus, mycophenolate, and methylprednisolone. Three animals received basiliximab induction; compared with nonsensitized animals, they showed a shorter mean survival time (4.7 ± 3.1 vs. 187 ± 88 days). Six animals were treated with T cell depletion (anti-CD4/CD8 mAbs), which prolonged survival (mean survival time 21.6 ± 19.0 days). All presensitized animals showed antibody-mediated rejection (AMR). In two of three basiliximab-injected animals, cellular rejection (ACR) was prominent. After T cell depletion, three of six monkeys experienced early acute rejection within 8 days with histological evidence of thrombotic microangiopathy and AMR. The remaining three monkeys survived 27–44 days, with mixed AMR and ACR. Most T cell–depleted animals experienced a rebound of DSA that correlated with deteriorating kidney function. We also found an increase in proliferating memory B cells (CD20⁺CD27⁺IgD⁻Ki67⁺), lymph node follicular helper T cells (ICOS⁺PD-1^hiCXCR5⁺CD4⁺), and germinal center (GC) response. Depletion controlled cell-mediated rejection in sensitized nonhuman primates better than basiliximab, yet grafts were rejected with concomitant DSA rise. This model provides an opportunity to test novel desensitization strategies.