Single and dual labelling of cytotoxic target cells. Comparison of three radioactive tracers, [35S]methionine, [75Se]selenomethionine, and chromium-51.
[75Se]selenomethionine (75SeM) has been shown to provide several advantages over Na(2)51CrO4 (51Cr) labelling of metabolizing target cells: high labelling efficiency and low spontaneous release of 75SeM-labelled target cells permit improved monitoring of cytotoxicity due to extended effector/target ratios in short- and long-term assays. Unfortunately, 75SeM will soon be difficult to obtain. Therefore we studied the suitability of [35S]methionine (35SM) as a substitute for 75SeM. Furthermore, we explored the potential of dual labelling of suspension target cells applying combinations of 35SM and 51Cr or 75SeM and 51Cr. 35SM is a suitable substitute for 75SeM retaining most of the advantages of 75SeM labelling. Although considerably higher labelling of cells is possible we obtained the most efficient labelling with 100-400 kBq/ml of 35SM or 75SeM resulting in a relatively high uptake (3-15 cpm/cell) and very low spontaneous release (1-2%/h) up to 24 h. This permits short- and long-term cytotoxic assays and the use of low numbers of target cells (1 x 10(3)) providing increased cytotoxic sensitivity with reduced amounts of effector cells. Suitable dual labelling of target cells with 35SM plus 51Cr or 75SeM plus 51Cr documented convincingly identical release kinetics for 35SM and 75SeM but partially discordant ones for 51Cr. Depending on the target cell used dual labelling permits discrimination and monitoring of different cytotoxic or release mechanisms in cellular cytotoxicity.
Immunology Unit, Veterinary School, Hannover, Germany.
J
J
Heymer
W
W
Leibold
D002860:Chromium Radioisotopes; D003601:Cytotoxicity Tests, Immunologic / Q000379:methods*; D006801:Humans; D008715:Methionine / Q000378:metabolism; D012644:Selenium Radioisotopes; D012645:Selenomethionine / Q000378:metabolism; D013462:Sulfur Radioisotopes
D002860:Chromium Radioisotopes; D012644:Selenium Radioisotopes; D013462:Sulfur Radioisotopes; D012645:Selenomethionine; D008715:Methionine