Table 1.

Early versus late acute AMR

	Early AMR	Late AMR
Timing	Days to weeks post-transplant	Months to years post-transplant
Pathophysiology	Levels of preformed DSA increase from memory B-cell response following antigen stimulation	Formation of De Novo DSA or increase in preformed DSA in setting of suboptimal immunosuppression and/or concomitant cellular rejection
Histology	C4d+ peritubular capillaries on immunofluorescence, acute tubular necrosis, peritubular capillaritis, and glomerulitis	Similar to early AMR in most cases: Peritubular capillaritis and glomerulitis +/− C4d positivity in setting of interstitial inflammation and tubulitis. Features of transplant glomerulopathy may also be present.
Treatment	Plasmapheresis IVIG Eculizumab Bortezomib Rituximab	Treatment of cellular rejection (ex. steroids and anti-lymphocyte therapy). Consider plasmapheresis and IVIG if DSA MFI > 6000. In absence of transplant glomerulopathy, eculizumab, bortezomib, or rituximab could be considered.