Infusion of IgG helps imaging antibodies from circulation

Now, David Scheinberg and colleagues at Memorial Sloan-Kettering Cancer Center, New York, have found a way to decrease the length of time IgG stays in the blood of both mice and humans such that tumor targeting is not compromised but the negative side effects of radiolabeled IgG are substantially diminished.

IgG hangs around in the blood for a long time because it is protected from degradation by the neonatal Fc receptor (FcRn). Infusing mice and humans with large amounts of polyclonal IgG after they had received a radiolabeled monoclonal antibody increased the rate of clearance of the radiolabeled monoclonal antibody from the blood. For both mice and humans, uptake of the radiolabeled monoclonal antibody by the tumor was the same with or without IgG infusion. However, the contrast between the labeled tumor and blood was much better with IgG infusion. Further analysis in mice also showed that IgG infusion decreased the normal tissue toxicity caused by the radiolabeled monoclonal antibody. The authors therefore suggest that polycloncal IgG infusion provides a new way to enhance the therapeutic and imaging efficacy of radiolabeled and toxin-conjugated monoclonal antibodies.-Journal of Clinical Investigation