Nonspecific human immunoglobulin G for imaging infection and inflammation: what did we learn?

Radiolabeled human non specific immunoglobulin G (IgG or HIG) was proposed in the early nineties as a potential tracer for imaging infection and sterile inflammation. Formulations with ¹¹¹In and (99m)Tc as the label were developed and extensive preclinical work was undertaken to assess its potential as a diagnostic agent. ¹¹¹In-HIG was used in a number of clinical studies and proved efficient in detecting orthopedic infections, especially in patients with prostheses, fever of unknown origin, opportunistic infections in immunocompromised patients, including patients infected with the human immunodeficiency virus and neutropenic patients. In the latter patients, there was no need for blood manipulation to harvest white cells for leukocyte labeling which was a considerable advantage. (99m)Tc-HIG was also successfully used for imaging sterile arthritis, especially rheumatoid arthritis. Two decades later, radiolabeled HIG is almost completely abandoned as a general purpose tracer for imaging infection and inflammation and this article aims to find out why this has happened.