Supplementary Material for: Efficacy of Double Membrane Filtration Immunoadsorption in Severe C1q-Binding Donor-Specific Antibody-Positive Acute Humoral Kidney Allograft Rejection: A Case Series

<b><i>Introduction:</i></b> Acute antibody-mediated rejection (ABMR) is an important threat to renal allograft survival in the early transplant period and the major single cause of graft loss in the first postoperative year. Semi-selective immunoadsorption (IA) remains one of the commonly applied treatments in ABMR, reducing allo-reactive antibody load. Adding double filtration plasmapheresis (DFPP) to IA might enhance therapeutic efficacy by also addressing innate humoral effectors like complement factors. <b><i>Methods:</i></b> Four patients with ABMR were treated with DFPP + IA. Clinical, histological, and immunological data and adverse events were retrospectively collected. <b><i>Results:</i></b> Here we present four high-risk treatment-refractory ABMR cases with C1q-binding donor-specific antibodies and histology of humoral rejection under treatment with DFPP + IA. While the earlier cases (within the first year after transplantation) showed marked reduction in ABMR severity and improvement of kidney function, the later cases did not respond accordingly. Late ABMR patient 1 stabilized, whereas late ABMR patient 2 did not respond to treatment. <b><i>Conclusions:</i></b> Our data support the consideration of DFPP + IA as a rescue treatment option in early, severe, high-risk ABMR cases in which other treatments failed.