Clearance of injected radioactively labelled antibodies to tumour products by liposome-bound second antibodies.
Liposomes containing anti-goat immunoglobulin were injected 24 h after administration of 125I-labelled goat antibody against the carcinoembryonic antigen (anti-CEA) to groups of nude mice bearing human tumour xenografts, and normal mice. Controls in each group received radioactively labelled anti-CEA only. In liposome-treated mice, blood 125I levels were lower than those of controls 30 min to 24 h after liposome administration, with corresponding accumulation of 125I activity in the liver and spleen for the first 2 h after liposome injection. [14C]Cholesterol or 99mTc labels in the bilayer were eliminated rapidly from the blood, with uptake in the liver and spleen. In xenograft-bearing mice, 125I activity detected in the tumours up to 6 h after liposome injection was identical to that detected in the tumours of controls. However, 24 h after liposome injection a reduction in the tumour concentration of 125I-labelled anti-CEA was obtained, but the tumour/blood radioactivity was still increased. In two mice given 27 mumol lipid, the blood radioactivity count after 24 h was only 5% of that in the controls. In rabbits, 2 h after administration of liposomes containing anti-goat second antibody, the circulating 125I activity had dropped by 28-40%. The results suggest that administration of liposome-entrapped second antibody approximately 2 h prior to external scintigraphy may clear circulating radioactively labelled primary antibody by up to 50%.
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D000912:Antibodies, Neoplasm / Q000378:metabolism*; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D007457:Iodine Radioisotopes; D008081:Liposomes; D008099:Liver / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000276:immunology*; D013154:Spleen / Q000378:metabolism
D000888:Antibodies, Anti-Idiotypic; D000912:Antibodies, Neoplasm; D002272:Carcinoembryonic Antigen; D007457:Iodine Radioisotopes; D008081:Liposomes