CASP3 and interstitial lung disease: Immunohistochemistry performed on these samples revealed increased caspase 3 cleavage in the fibrotic samples (Figure 4a, b and data not shown) and a nearly twofold increase in TUNEL staining in both the IPF samples and CTD-ILD samples when compared to non-fibrotic control (P < 0.05 both comparisons, Figure 4c-e).