Addition of granzyme A (GrA) to EDTA plasma results, in the presence of heparin, in GrA-antithrombin III (ATIII) complex formation and a decrease in antigenic recovery.

GrA (18 ng) was incubated with 5 μL of EDTA-plasma either in or not in the presence of 10 U of heparin for 30 minutes at 20°C. As a control, GrA was also incubated with plasma containing 0.1 mol/L benzamidine. Before analysis, the samples were diluted to a final concentration of 7.5 ng/mL GrA. (A) GrA-ATIII complexes and (B) antigenic GrA present in the mixtures were measured and represented as described in the legend for Figure 2.