Detection of granzyme B activity in PMNs. (A) Lysates of freshly isolated PMNs (5 × 10; (▴) contained enzyme activity measured by cleavage of the chromogenic substrate Boc-Ala-Ala-Asp-pNA. Lysates of unstimulated PMNs (•) or of PMNs cultivated for 24 hours with IFN-γ (100 U/mL; ▪) contained less enzymatic activity. (B) PMN lysates were adsorbed to mouse IgG or antigranzyme B; then substrate conversion was measured as increase of optical density (OD) in 3 dilutions. In parallel, granzyme B adsorbed to the antibody-coated beads was determined by quantitative cytofluorometry (data represent mean of triplicates).