Localization of Fc and Fab fragments of nonspecific polyclonal IgG at focal sites of inflammation.
Intact IgG, Fc, Fab, and 1/2Fc (reduced and alkylated Fc) were coupled to DTPA, labeled with indium-111 and administered to rats to compare the ability of fragments of IgG to localize at focal sites of inflammation. Two sets of experiments were performed: First, 1, 6, 24, and 48 hr after injection, biodistribution was determined in healthy animals; second, localization at sites of inflammation was determined by scintillation camera imaging of animals with deep-thigh infection due to Escherichia coli. The biodistribution studies demonstrated differences in kidney and liver localization: IgG less than Fc less than Fab less than 1/2Fc (kidney), Fc less than 1/2Fc less than IgG less than Fab (liver). The imaging studies revealed that target-to-background ratio (T/B) and percent residual activity (%RA) for IgG was significantly greater (p less than 0.01) than 1/2 Fc or Fab, and T/B for IgG was greater (p less than 0.01) than Fc. These studies suggest that the Fc portion of IgG is the fragment with the best imaging properties.
Fischman
A J
AJ
Department of Radiology, Massachusetts General Hospital, Boston 02114.
Rubin
R H
RH
White
J A
JA
Locke
E
E
Wilkinson
R A
RA
Nedelman
M
M
Callahan
R J
RJ
Khaw
B A
BA
Strauss
H W
HW
D000818:Animals; D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D007205:Indium Radioisotopes; D007249:Inflammation / Q000000981:diagnostic imaging* / Q000276:immunology; D008099:Liver / Q000000981:diagnostic imaging; D008297:Male; D011877:Radionuclide Imaging; D051381:Rats; D011919:Rats, Inbred Strains; D013154:Spleen / Q000000981:diagnostic imaging
D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D007205:Indium Radioisotopes