Isolation and labelling of human leukocytes with 99mTc.

The role of the leukocyte isolation procedure on cell labelling with 99mTc has been evaluated. Separation of leukocytes was performed by two procedures: sedimentation on methyl cellulose, followed by discontinuous gradient centrifugation; methyl cellulose sedimentation and hypotonic haemolysis of residual red blood cells. After washing the cells in saline and incubation with a stannous pyrophosphate agent, the leukocytes were labelled with 5-10 mCi 99mTc. Procedure 1 gave a higher purity but lower recovery of polymorphonuclear leukocytes, and a minor contamination of red blood cells. 99mTc labelling of cells was slightly more efficient with this method, probably due to the presence of red blood cells. Procedure 1 is recommended for in vitro studies on cell kinetics and procedure 2 is recommended for clinical use.