[en] A brief review is given of the developments in labelling human leucocytes for diagnostic imaging studies. These include the non-selective cell-labelling agents such as ¹¹¹In oxine which label mixed leucocytes, separation methods to produce ¹¹¹In-labelled granulocytes, and labelling mixed leucocytes with ⁹⁹Tc^mHMPAO. The search for selective cell-labelling agents is also discussed; the main hope lies with monoclonal antibodies. (U.K.)

[en] ⁹⁹Tcsup(m)-hexamethyl propylene amine oxime (⁹⁹Tcsup(m)-HM-PAO) has been evaluated as an agent to radiolabel human platelets in vitro. The rate of uptake of this lipophilic complex, the effect of HM-PAO, plasma and platelet concentration were measured to determine the optimum conditions for radiolabelling platelets for short-term clinical investigations of thromboses. The complex was made according to the manufacturer's instructions and immediately added to isolated platelets in vitro. The rate of labelling was slower than for leucocytes, reaching a plateau after approximately 40 min at room temperature. Increasing the temperature to 37⁰C did not increase the labelling efficiency (LE). Addition of plasma to platelets at a cell concentration of 1 x 110⁹ ml^-1 reduced the LE from 66% in saline to 52% in 20% ACD-plasma. However, increasing the platelet concentration from 5 x 10⁸ to 2 x 10⁹ ml^-1, increased the LE from 9 to 76% for platelets labelled in 20% plasma for 30 min at RT. The in vitro stability of the ⁹⁹Tcsup(m) in the labelled cells showed that 7% of the radioactivity was immediately released from the platelets and a further 13% was eluted during a 60 min incubation in plasma at 37⁰C. It has been concluded that incubation of platelets with ⁹⁹Tcsup(m)-HM-PAO containing 80 μg ml^-1 HM-PAO at a cell concentration of 1 x 10⁹ ml^-1 or greater, results in a high LE, with more than 85% of the ⁹⁹Tcsup(m) being retained by the platelets during a 60 min incubation in plasma. (author)

[en] In this paper, several aspects of the In-111 labelling techniques of blood cells are considered like In-111 tropolonate preparation; cell separation of erythrocytes, platelets and granulocytes; in vitro cell labelling and its efficiency. (Auth.)

[en] Rat thoracic-duct lymphocytes and HeLa S3 cells were labeled in vitro with different amounts of indium-111 oxine. The labeled rat lymphocytes were tested for their ability to recirculate normally in syngeneic rats; the labeled HeLa S3 cells for their ability to divide to form colonies in tissue culture. Both cell types behaved normally by these criteria when labeled with small amounts of indium-111 oxine but at higher doses were obviously damaged. Evidence was obtained for the HeLa S3 cells that this damage was primarily radiation-induced. These findings may impose limitations on the use of In-111 oxine as a cell label for clinical purposes

[en] A simple and rapid in vitro procedure has been developed for selectively radiolabelling erythrocytes in whole blood using ^113mIn-tropolonate. A maximum labelling efficiency of 97% was achieved, of which 95.5% was on the erythrocytes after only 5 min incubation of whole blodd at room temperature. The optimum amount of tropolone for labelling whole blood was 10 μg of tropolone per ml of blood using acid-citrate dextrose (ACD) as the anticoagulant and 50 μg of tropolone per ml of blood using heparin. Under these optimim conditions, only 2.5% of the cell-bound ^113mIn was released from the labelled cells during a 1 h in vitro incubation in cell-free plasma, irrespective of the anticoagulant used. These results suggest that ^113mIn-tropolonate may prove to be useful in vitro agent for labelling erythrocytes for short-term clinical investigations, especially at centres where ^99mTc and ¹¹¹In are unavailable. (author)

[en] The effect of acid-citrate-dextrose (ACD) and heparin on the labelling efficiency (LE) and optimum concentration of ligand required to radiolabel human granulocytes in plasma with ¹¹¹In-tropolonate or ¹¹¹In-2-mercaptopyridine-N-oxide (¹¹¹In-merc) has been measured. The concentrations of ligand (tropolone or merc) required for maximum cell labelling in plasma containing ACD were 4 x 10^-4 M tropolone and 1 x 10^-4 M merc, whereas using plasma containing heparin, the optimum concentrations were 10-fold higher, at 4 x 10^-3 M and 1 x 10^-3 M respectively. At the optimum ligand concentrations, the LE for 1 x 10⁸ granulocytes labelled in plasma containing ACD was 90% using ¹¹¹In-tropolonate and 82% using ¹¹¹In-merc, whereas using plasma containing heparin they were 68% and only 20%, respectively. Addition of ACD to heparinised plasma abolished the necessity for more ligand and increased the LE to the same values as those for plasma containing ACD alone. These results clearly demonstrate that to obtain a high LE using the lowest possible concentrations of tropolone or merc, the granulocytes must be labelled in plasma containing ACD. (author)

[en] The potential use of radio-iodinated monoclonal antibody cells as cell-labelling agents is discussed with particular reference to the preparation, radio-labelling and storage of monoclonal antibodies, their clinical applications, problems and future prospects. (U.K.)

[en] The labelling of HeLa S3 cells with ¹¹¹In acetylacetone (¹¹¹In-acac) was studied together with cell damage, measured by the reduction in colony-forming ability of labelled cells. Using 2 x 10⁵ cells/ml in Hepes saline buffer at pH 7.6 incubated with 7.4-185 kBq (0.2-5.0 μCi)/ml ¹¹¹In-acac, containing 0.19% acetylacetone for 15 minutes at room temperature, 60-80% ¹¹¹In was bound to the cells. The cell binding was linear with activity and resulted in an exponential reduction in colony forming ability and a D₀ of 26 kBq (0.7 μCi)/2 x 10⁵ cells. Radiation was shown to be the major cause of cell damage. It is concluded that ¹¹¹In-acac is preferable to ¹¹¹In oxine because it is soluble in physiological buffers, which eliminates the use of ethanol; it is quick and easy to prepare; and compared with previous results using HeLa S3 cells labelled with ¹¹¹In oxine, ¹¹¹In-acac gives much more reproducible results and is no more toxic. Clinically, ¹¹¹In-acac was shown to give similar results to ¹¹¹In oxine. (author)

[en] In this study, 2-[¹⁸F]fluoro-2-deoxy-D-glucose, ([¹⁸F]FDG) was used to radiolabel human granulocytes in vitro for possible clinical use by positron emission tomography (PET). Uptake of [¹⁸F]FDG was dependent on the amount of glucose in the labelling medium, eg. when 1 x 10⁷ granulocytes were incubated with [¹⁸F]FDG containing 15μg/mL glucose 80% of [¹⁸F]FDG was incorporated within 30 min, but in the presence of 1 mg/mL of glucose it was reduced to 2%. Increasing the cell concentration and activating the granulocytes with Streptococcus pneumoniae, opsonized zymosan or phorbol myristate acetate all increased the uptake of [¹⁸F]FDG. Retention of the [¹⁸F]FDGby the cells as [¹⁸F]FDG-6-phosphate was also dependent on the extracellular glucose concentration, 9% was released within 60 min in the absence of glucose, but 27% in the presence of 1 mg/mL glucose. (Author)

No abstract available