18F-FDG labelled leukocytes in vitro functional tests: Viability, chemotaxis and phagocytosis assays

Abstract

Purpose: 18F-FDG labelled leukocytes using PET/CT have been suggested as a radiotracer that offer specificity and high quality images for localization of inflammation and infection. The purpose of this in vitro study was to determine the functional integrity of leukocytes after labelling with 18F-FDG. Materials and Methods: Leukocytes were separated from whole blood donated by 6 healthy volunteers and labelled with 18F-FDG. The tests included viability, chemotaxis and phagocytosis of the cells. Trypan Blue was used for viability test. Directional migration was done using chemotaxis under agarose technique. Opsonised zymosan particles were used for phagocytosis assay. Results: Average labelling efficiency (LE) was 90.8%. Viability of 18F-FDG labelled leukocytes one hour after labelling was superior to 99%. Chemotaxis assay showed cells were attracted by chemoattractant after 4 hours of incubation. Labelled cells were found to continue further migration after 24 hours with approximately the same pattern and distance as those of unlabelled cells. Zymosan particles were phagocytosed by the labelled leukocytes. Conclusion: Our study showed that 18F-FDG labelled leukocytes preserved their functional integrity. The labelled cells were viable, responded to inflammatory signals and reacted by engulfing zymosan particles. The results of these in vitro tests suggest that 18F-FDG labelled leukocytes could be used for localization of infections and inflammations. © Lafont et al.