In vitro and in vivo evaluation of granulocyte labeling with [99mTc]d,1-HM-PAO.

The functional integrity of white blood cells labeled with [99mTc]d,1-HM-PAO containing variable amounts of the ligand or of the 99mTc activity was evaluated by enzymatic tests and by measuring random migration, chemotaxis, phagocytosis, killing, and adhesion. The ultrastructure of labeled cells was studied by electron microscopy. The tracer dose and the HM-PAO concentration did not significantly affect phagocytosis and killing. The results of the other tests remained normal. A maximum labeling efficiency of 80% was reached by incubating the granulocytes for 20 min with 10-20 mCi of [99mTc]d,1-HM-PAO containing 50 micrograms of the ligand in 1 ml of saline. There was only a slow washout of 20% of activity from the labeled cells in 24 hr. The ultrastructure was not influenced by the labeling technique. Proven infection sites of 17 orthopedic patients were clearly visualized. After a short transient lung uptake, there was a clear spleen and moderate liver uptake with early bladder and late prominent colon visualization. Because of the lower cost, favorable radiation dose and more suitable tracer characteristics, this technique is a promising alternative for 111In labeling of white blood cells.