Cytotoxic effect of radiolabeled C5a on U937 cells in vitro.
We studied whether the receptor (R) for C5a could be exploited to deliver the radiolabeled ligand into U937 cells. A dose-response for uptake of 125I-C5a was demonstrated. Incorporation of [3H]leucine by unstimulated or gamma-INF-stimulated U937 cells treated with 125I-C5a, was significantly lower compared with cells treated with 125I alone. Trypan blue exclusion experiments indicated that gamma-INF stimulated cells incubated with 125I-C5a were less viable than cells exposed to 125I or C5a alone. The results suggest that 125I-C5a is internalized into myeloid cells via C5a-R and is more cytotoxic in vitro than the radiolabel alone, but only at/above a specific activity of 4 microCi/microg.
Hetland
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Institute of Immunology and Rheumatology, The National Hospital, Oslo, Norway.
Hugli
T E
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D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D015936:Complement C5a / Q000493:pharmacokinetics*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D007930:Leucine / Q000493:pharmacokinetics; D009363:Neoplasm Proteins / Q000378:metabolism; D011951:Receptors, Complement / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects
D007457:Iodine Radioisotopes; D009363:Neoplasm Proteins; D011951:Receptors, Complement; D015936:Complement C5a; D007371:Interferon-gamma; D007930:Leucine