Chemotaxis, viability, and labeling stability of leukocytes labeled with (99m)Tc-exametazime stabilized with methylene blue.

Abstract

The in vitro viability, chemotaxis, and labeling stability of leukocytes labeled using (99m)Tc-exametazime stabilized with methylene blue were evaluated and compared with those obtained using nonstabilized (99m)Tc-exametazime. Two identical leukocyte populations, from 30 healthy donors, were labeled simultaneously using freshly prepared and 2-h-old stabilized (99m)Tc-exametazime. The following quality control techniques were performed on each labeled leukocyte sample: eosin Y staining, chemotaxis radioassay, and labeling stability at 2 h after labeling. Eosin Y staining showed a cell viability of at least 98% in all samples, without a significant statistical difference between the populations. Chemotactic indices obtained with leukocytes labeled with freshly prepared, unstabilized (99m)Tc-exametazime were statistically greater than those obtained using (99m)Tc-exametazime stabilized with methylene blue (z = 2.41; P<0.02). Labeling stability at 2 h after labeling was the same for both populations. The use of (99m)Tc-exametazime stabilized with methylene blue for leukocyte radiolabeling does not affect either cell membrane integrity or labeling stability but can cause a decrease in the cell chemotactic capacity that discourages its clinical use.