*Purpose: Antibody-mediated rejection (AMR) has been defined by an expert pathology group in 2011 which resulted in the ISHLT pathologic AMR (pAMR) grading scale. The presence of donor-specific antibodies (DSA) were not included as these were reported not to have a high association with this grading scale. However, in the current era of newer immunosuppression and better antibody detection techniques, it is not clear if this is still the case. Therefore, we sought to assess the presence of DSA by single antigen via the Luminex platform in the current era of 2015 to 2020.

*Methods: Between November 2015 and November 2020, we assessed 39 heart transplant patients and assessed the patients who had first year pAMR1, pAMR2, or pAMR3. The entire group was assessed for the presence of DSA 1 to 2 weeks before or after the biopsy was performed.

*Results: DSA was present in 35.7% of the patients with pAMR1 and in 84.0% of the patients with pAMR2. There was no significant difference between the two groups in the mean ejection fraction at the time of biopsy and mean maximum mean fluorescence intensity (MFI) of DSA found in patients. Of note, the mean maximum MFIs were in the strong binding range. There were no patients with pAMR3.

*Conclusions: Presence of DSA appears to be more associated with pAMR2 and less with pAMR1. This data underscores the antibody involvement of pAMR2. Larger studies to assess clinical outcome will be paramount.

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