Exocytosis and macrophage-mediated antibody-dependent cellular cytotoxicity: a cautionary note.
The appearance of soluble radioisotope from macrophages (M phi) that previously had ingested 51Cr-labelled antibody-coated sheep erythrocytes (51Cr-EA) was assessed to determine if exocytosis contributed to the pool of radioactivity used to measure antibody-dependent cellular cytotoxicity (ADCC). M phi preloaded for 60 min with 51Cr-EA lost the majority of the ingested 51Cr over a subsequent 3 hr incubation period. The exocytotic rate was independent of the number of 51Cr-EA ingested, but was temperature dependent with no appreciable release of 51Cr observed at 4 degrees. The exocytotic process was unaffected by sodium azide (10 mM) but was markedly enhanced in the presence of iodoacetate (50 mM), cytochalasin B (20 micrograms/ml) or lidocaine (0.5 mM). The results show that M phi rapidly digest engulfed target cells and that exocytosis can contribute sufficient soluble radioactivity to the extracellular pool to lead to misinterpretation of putative ADCC activity.
D000818:Animals; D000920:Antibody-Dependent Cell Cytotoxicity; D000963:Antimetabolites / Q000494:pharmacology; D002452:Cell Count; D002478:Cells, Cultured; D002860:Chromium Radioisotopes; D005089:Exocytosis / Q000187:drug effects; D005260:Female; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010587:Phagocytosis; D013696:Temperature; D013997:Time Factors
D000963:Antimetabolites; D002860:Chromium Radioisotopes