CTSB and idiopathic pulmonary fibrosis: Western blot analysis of lung lysates showed that CTSB was significantly up-regulated in the advanced IPF group compared to the control and early IPF groups (control 3 vs. early IPF 5 vs. advanced IPF 4, 1 vs. 31.2 vs. 204, p < 0.001, Figure 3G,H).