On the basis of preliminary proteomic approach to plasmapheresis eluates from patients with abrupt recurrence of proteinuria after a renal graft, and of the recent description of agonistic anti-CD40 antibodies in FSGS patients [14], we hypothesized that sCD40L could act as a permeability trigger of recurrence. This evidence concerns the gene CD40 and focal segmental glomerulosclerosis.