CASP3 and chronic obstructive pulmonary disease: Analysis of peripheral lung tissue by immunostaining for cleaved caspase 3 and pro-SFTPC demonstrated increased frequency of cleaved caspase 3 expression in pro-SFTPC positive cells (17% ± 5.5%, mean ± SD) compared with non-AATD tissue (3.1% ± 3.2% in wild-type COPD and 3.9% ± 3.3% in healthy control participants with no COPD) (Fig 2I-J).