Focal segmental glomerulosclerosis (FSGS) is a glomerular histopathological lesion of some but not all glomeruli. FSGS is frequently associated with heavy proteinuria and progressive renal failure requiring dialysis or kidney transplantation. However, primary FSGS also has 40-80% risk of recurrence of disease in the transplanted kidney (rFSGS). Sera from patients with primary FSGS causes podocyte injury in culture but the injury is heterogeneous. Multiple circulating factors have been proposed to contribute to the pathogenesis of primary and rFSGS. However, neither the factors nor the downstream effectors specific to individual factors have been identified. The TNF pathway activation by one or more circulating factors present in the sera of patients with FSGS has been supported by multiple studies. Several studies have suggested a causative role for soluble urokinase-type plasminogen activator receptor (suPAR) and CD40 autoantibody in the development and recurrence of FSGS. Anti uPAR antibodies have been shown to block suPAR induced renal injury in mouse models of FSGS and commercially available anti CD40 antibodies block the development of proteinuria in mice injected with suPAR and CD40 autoantibodies purified from rFSGS patients (CD40Ab). Here we show that the podocyte injury caused by sera from FSGS patients is at least in part mediated by CD40 and suPAR by blocking the podocyte actin depolarization with a novel anti uPAR antibody (2G10) as well as a humanized commercial CD40 antibody (BMS). Additionally, we compare the molecules and pathways activated in response to CD40Ab from rFSGS patients and suPAR to that of TNFα and delineate the unique pathways associated with FSGS injury.