CD40 and renal fibrosis: Applying the Goldblatt two-kidney, one-clip (2K1C) model of ischemic renal disease in the Dahl S rats, in which a surgical clip (0.2 mm internal diameter) is placed around the left renal artery to induce ischemic renal injury, we reported significantly elevated levels of CD40 expression in the cortex of the ischemic kidney with extensive renal fibrosis [18].