Highly-sensitive SAB improved posttransplant monitoring of DSA in kidney transplant. AMR-GL was associated with total DSA in combination with T-cell activation pretransplant and de novo or persistent C1q-binding DSA posttransplant. Posttransplant presence of persisting or de novo HLA antibodies, especially if strong and C1q-fixing is associated with graft loss, even if the antibodies are not specific for mismatched donor HLA. Patients with pre-transplant DSA and an activated immune system appear to require special attention after kidney transplantation.