Neutrophil elastase in bone marrow cells from wild-type (+/+), heterozygous (+/−), and serglycin knockout (−/−) mice. (A) Elastase activity measured by spectrophotometry following the degradation rate for methoxysuccinyl-Ala-Ala-Pro-Val-P-nitroanilide. The SLPI-inhibitable activity is expressed as absorbance change per minute at 405 nm. Median is indicated by bold line and range by whiskers. The asterisk signifies statistically significant difference at the 5% level, log₁₀-transformed data, independent t test; +/+, n = 3; +/−, n = 4; −/−, n = 6. (B) Western blotting of bone marrow cell lysates. The 2 blots have been loaded and processed in parallel; the lower blot has been incubated with rabbit anti–murine neutrophil elastase (NE), and the upper blot has been incubated with monoclonal mouse anti–murine β-actin (Ac) for loading control. Molecular weight markers are indicated. (C) Northern blotting with a full-length probe for murine neutrophil elastase; the blot is the same as in Figure 1 after stripping and reprobing with the neutrophil elastase probe. (D-E) Immunocytochemistry for neutrophil elastase in murine bone marrow cells from wild-type mice (D) and serglycin^−/− mice (E); bar, 20 μm. Rarely a promyelocyte from serglycin^−/− mice stains positive for neutrophil elastase (E, inset).