Antibody‐mediated rejection as a contributor to previously unexplained early liver allograft loss

We analyzed 60 patients with idiopathic early allograft loss (defined as death or retransplantation <90 days) to determine the relative contribution of preformed donor specific HLA alloantibodies (DSA) to this endpoint and defined strict criteria for the diagnosis of antibody-mediated rejection (AMR) in liver allografts. Inclusion criteria encompassed availability of a pre-transplant serum sample and both post-reperfusion and follow-up tissue specimens for “blinded” retrospective re-review of histology and C4d staining. AMR was diagnosed based on the presence of all 4 strict criteria: 1) DSA in serum; 2) histopathological evidence of diffuse microvascular injury/microvasculitis, consistent with antibody-mediated injury; 3) diffuse C4d staining in the portal microvasculature with or without staining in the sinusoids or central veins in at least one sample; and 4) exclusion of other causes of a similar type of injury. Patients thought to be experiencing definite AMR on the basis of routine histopathology alone showed the highest levels of DSA sensitization. Forty percent of patients with pre-transplant DSA with a pattern of bead saturation after serial dilutions developed AMR. One additional multiparous female developed, what appeared to be, a strong “recall” response resulting in combined AMR and ACR causing graft failure. A contribution of DSA to allograft failure could not be excluded in three additional patients who received marginal grafts. In conclusion, liver allograft recipients with high mean fluorescence intensity (MFI) preformed DSA despite dilution seem to be at risk for clinically significant allograft injury, and possibly loss, from AMR often in combination with ACR.