A renal transplant recipient develops de novo donor-specific antibodies (DSA) against HLA-DQ7 at 18 months post-transplant, with a mean fluorescence intensity (MFI) of 4,500 on single-antigen bead assay. Which additional DSA characteristic would MOST significantly stratify this patient's risk for progressive antibody-mediated rejection (AMR) and graft loss?

Remaining questions and full explanations are VIP-exclusive.