FUNCTIONAL UP-REGULATION OF GRANULOCYTES LABELED WITH TECHNETIUM-99M-HMPAO AND INDIUM-111-OXINATE

Indium-111-oxinate-labeled granulocytes have been used in vivo for sev eral years for the detection of abscesses, Technetium-99m-hexa methylp ropyleneamine oxime (Tc-99m-HMPAO) labeling has more recently been des cribed. Methods: The influence of radiolabeling by both radiotracers o n adhesion glycoprotein CD11b quantification was studied in quiescent and formyl-methionylleucylphenylalanine (fMLP)-activated neutrophils ( PMN). Adhesion was assessed on human umbilical endothelial cells (HUVE C) as well as the repercussion of the granulocyte labeling on HUVEC vi ability (neutral red) and metabolic activity (MTT). Chemotaxis of PMN was evaluated by measuring migration under agarose with fMLP as chemoa ttractant We also measured phagocytosis and the production of hydrogen peroxide induced by staphylococcus aureus. Results: Whereas whole fun ctional integrity is maintained after labeling, most of the functions (CD11b expression, adhesion, HUVEC metabolic activity) are up-regulate d while chemotaxis is decreased in the presence of both radiotracers. Indium-111-oxinate induces larger alterations than Tc-99m-HMPAO. Concl usion: These data were obtained in normal volunteers, In patients, alt erations due to the in vitro labeling procedure, in addition to potent ial functional alterations caused by the underlying pathology, should be taken into account during image interpretation.