Expression of caspase-14 and (pro)filaggrin in wild-type and caspase-14–deficient skin. Immunofluorescence staining for caspase-14 (red) and (pro)filaggrin (green) on paraffin sections of 5.5-d-old skin of both wild-type (+/+) and caspase-14–deficient (−/−) mice (Denecker et al., 2007). Nuclei are counterstained with DAPI. Fluorescence microscopy was performed on a CellM system (Olympus) with an upright microscope (BX61; Olympus). Observation was performed with a 60× 1.42 NA oil objective. A specific DAPI emission band-pass filter (450–470 nm) and a GFP emission band-pass filter (510–550 nm) were used. Image acquisition and processing were performed with the CellM software using a cooled CCD camera with a 1,344 × 1,024 pixel resolution. Image intensity scaling and color conversion were completed in ImageJ (National Institutes of Health). The dotted lines indicate the outer borders of the stratum corneum. Caspase-14 is expressed mainly in the spinous, granular, and cornified layers of wild-type mice and is absent in caspase-14–deficient mice. (Pro)filaggrin is expressed in the granular layer and in the lower cornified layer in wild-type skin. In caspase-14–deficient skin, additional filaggrin immunoreactive fragments are detected in the upper layers of the stratum corneum.