Evaluation of monoclonal immune complexes and microaggregated albumin as inhibitors of uptake and labeled monoclonal antibody by hepatic tissue

Hepatic uptake of labeled monoclonal antibody (MoAb) remains a persistent problem. Human hepatoma tumors were transplanted into adult rats and successfully imaged following the injection of In-111-antiferritin MoAb. Biodistribution studies revealed that the livers in both tumor and non-tumor bearing rats accumulate and retain labeled MoAb. Two biodegradable agents thought capable of inhibiting the uptake of MoAb by blocking the liver RES were studied. Immune complexes of human spleen ferritin and antiferritin-MoAb were prepared in vitro and tested as liver RES blocking agent to the same labeled/MoAb and labeled MoAb-ferritin complex. A preparation of microaggregated albumin with an average sphere diameter of 0.4 microns (range 0.1-5.0) was tested. These compounds were injected 30 minutes prior to the injection of labeled MoAb or MoAb:Ag complex; 2-4 rats per treatment group. All agents failed to inhibit or alter the uptake of labeled MoAb and MoAb:Ag complex at concentrations of 500 μg/rat of cold complex and 250 and 500 μg/rat of microaggregated albumin. Rats with no pretreatment showed a 38% uptake. Pretreatment with complex showed 45% uptake Microlite 43% uptake, and cold complex 46% uptake. Pretreatment with 12 mg of microaggregated albumin also failed to inhibit hepatic uptake of /sup 99m/Tc-Microlite and /sup 99m/Tc sulfur colloid. These data indicate that hepatic uptake of labeled MoAB is not the result of macrophage activity in the hepatic sinusoids