title: Radioimaging of experimental glioma grafts using F (ab')2-fragments of monoclonal antibodies.
abstract: Iodinated F (ab')2-fragments of monoclonal IgG2a-antibodies (McAbs) 14 AC1 raised against membrane components of an experimental rat glioma (79FR-G-41) were used for the radioimmunodetection of glioma xenografts in athymic mice. For gamma imaging, nude mice with intramuscular glioma grafts received 10-20 micrograms of 131I-labelled whole immunoglobulins and F (ab')2-fragments of the 14AC1 McAb, respectively, with an activity of 50-150 mu Ci (1.85-5.55 MBq). Scans obtained at 24, 48, 72 and 96 hours after injection demonstrated tumor accumulation of F (ab')2-fragments at 24 hours, and adequate tumor visualization without background subtraction at 48 hours. The rapid blood clearance of F (ab')2-fragments resulted in a whole body half life of 6 hours. Scintigrams using intact antibody provided comparable tumor localization at 96 hours, but also high bloodpool radioactivity and a half life period of more than 4 days. 131I-labelled normal mouse-IgG as control for non-specific uptake of immunoglobulins in the tumor revealed no tumor visualization at any time. Rapid tumor permeation, short blood clearance and a markedly reduced background radioactivity let F (ab')2-fragments appear superior to whole immunoglobulins in immunoscintigraphy, thus indicating their potential value for the improvement of radioimmunodiagnosis of glioma disease.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D005260:Female; D005910:Glioma / Q000000981:diagnostic imaging*; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D008297:Male; D008722:Methods; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011877:Radionuclide Imaging; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments